Exchange Server 中的邮件大小限制Message size limits in Exchange Server

你可以对经过组织的邮件应用限制。可以将整个邮件的最大大小设置为一个整体,或设置为邮件各个部分的大小,或同时设置为两者。例如,可以限制邮件头或附件的最大大小,或者设置可以添加到邮件的收件人的最大数目。可以将这些限制应用到整个 Exchange 组织、特定邮件传输连接器、特定服务器和单个邮箱。You can apply limits to messages that move through your organization. You can set the maximum size of an entire message as a whole, or the size of individual parts of a message, or both. For example, you could restrict the maximum size of the message header or attachments, or set a maximum number of recipients that can be added to the message. You can apply these limits to your entire Exchange organization, to specific mail transport connectors, specific servers, and to individual mailboxes.

此主题仅探讨有关邮件和收件人大小的限制。This topic only talks about message and recipient size limits. 如果您想详细了解如何控制一段时间内发送的邮件数、允许的一段时间内连接数以及在关闭连接之前 Exchange 将等待的时间,请参阅邮件速率限制和限制If you want to know more about how to control how many messages are sent over time, how many connections are allowed over time, and how long Exchange will wait before closing a connection, see Message rate limits and throttling.

在规划 Exchange 组织的邮件大小限制时,请考虑以下问题:As you plan the message size limits for your Exchange organization, consider the following questions:

  • 对所有传入邮件的大小限制应为多少?What size limits should I impose on all incoming messages?

  • 对所有传出邮件的大小限制应为多少?What size limits should I impose on all outgoing messages?

  • 组织的邮箱配额以及如何将所选择的邮箱大小限制与邮箱配额大小相关联?What is the mailbox quota for my organization, and how do the message size limits that I have chosen relate to the mailbox quota size?

  • 组织中是否存在需要收发大于最大允许大小的邮件的用户?Are there users in my organization who need to send or receive messages that are larger than the maximum allowed size?

  • 组织是否包括要求不同邮件大小限制的其他邮件系统或独立业务单位?Does my organization include other messaging systems or separate business units that require different message size limits?

本主题提供指导来帮助你回答这些问题,并在适当的位置应用相应的邮件大小限制。This topic provides guidance to help you answer these questions and to apply the appropriate message size limits in the appropriate locations.

邮件大小限制的类型Types of message size limits

以下列表描述了邮件大小限制的基本类型,以及将应用这些限制的邮件组件。The following list describes the basic types of message size limits, and the message components that they apply to.

  • 整个邮件大小限制:指定邮件的最大大小,包括邮件头、邮件正文和任何附件。Whole message size limits: Specifies the maximum size of a message, which includes the message header, the message body, and any attachments. Exchange 使用自定义 X-MS-Exchange-Organization-OriginalSize: 邮件头在邮件进入 Exchange 组织时记录其原始邮件大小。Exchange uses the custom X-MS-Exchange-Organization-OriginalSize: message header to record the original size of the message as it enters the Exchange organization. 只要检查邮件大小,就会使用当前邮件大小或原始邮件大小头的较低值。Whenever the message size is checked, the lower value of the current message size or the original message size header is used. 邮件的大小可能会由于内容转换、编码和传输代理处理等原因而有所变化。The size of the message can change because of content conversion, encoding, and transport agent processing.

    对于任何邮件大小限制,您设置的值都必须大于要强制应用的实际邮件大小。这样就可以对附件和其他二进制数据进行 Base64 编码了。由于 Base64 编码会导致邮件大小增加约 33%,因此您指定的值应比要强制应用的实际邮件大小高出约 33%。例如,如果您指定的最大邮件大小值为 64 MB,则可以预计实际最大邮件大小值约为 48 MB。For any message size limit, you need to set a value that's larger than the actual size you want enforced. This accounts for the Base64 encoding of attachments and other binary data. Base64 encoding increases the size of the message by approximately 33%, so the value you specify should be approximately 33% larger than the actual message size you want enforced. For example, if you specify a maximum message size value of 64 MB, you can expect a realistic maximum message size of approximately 48 MB.

  • 附件大小限制:指定邮件中单个附件的最大大小。Attachment size limits: Specifies the maximum size of a single attachment in a message. 邮件中可能会包含许多较小附件,这样会大大增加邮件的总体大小。The message might contain many smaller attachments that greatly increase its overall size. 但是,附件大小限制仅适用于单个附件的大小。However, the attachment size limit applies only to the size of an individual attachment. 虽然不能限制邮件的附件数,但可以使用最大邮件大小限制来控制邮件总附件的最大值。While you can't limit the number of attachments on a message, you can use the maximum message size limit to control the maximum total of attachments on the message.

  • 收件人限制:指定邮件中允许的收件人总数。Recipient limits: Specifies the total number of recipients that are allowed in a message. 其中包括 To:Cc:Bcc: 字段中的收件人总数。This includes the total number of recipients in the To:, Cc:, and Bcc: fields. 一个通讯组将被视为一个收件人。A distribution group counts as a single recipient.

  • 邮件头大小限制:指定邮件中所有邮件头字段的最大大小。Message header size limits: Specifies the maximum size of all message header fields in a message. 不考虑邮件正文或附件的大小。The size of the message body or attachments isn't considered. 因为邮件头字段是纯文本,所以邮件头的大小由每个邮件头的字符数和邮件头字段的总数确定。Because the header fields are plain text, the size of the header is determined by the number of characters in each header field and by the total number of header fields. 每个文本字符占用 1 字节。Each text character consumes 1 byte.

限制的作用域Scope of limits

下表显示了组织、连接器、服务器和邮箱级别的邮件限制,其中包括有关如何在 Exchange 管理中心 (EAC) 或 Exchange 命令行管理程序 中配置这些限制的信息。The following tables show the message limits at the Organization, Connector, Server, and Mailbox levels, including information about how to configure the limits in the Exchange admin center (EAC) or the Exchange Management Shell. 若要了解如何在本地 Exchange 组织中打开 Exchange 命令行管理程序,请参阅 Open the Exchange Management ShellTo learn how to open the Exchange Management Shell in your on-premises Exchange organization, see Open the Exchange Management Shell.

组织限制Organizational limits

组织限制适用于组织中存在的所有 Exchange 2019 服务器、Exchange 2016 服务器、Exchange 2013 邮箱服务器和 Exchange 2010 集线器传输服务器。Organizational limits apply to all Exchange 2019 servers, Exchange 2016 servers, Exchange 2013 Mailbox servers, and Exchange 2010 Hub Transport servers that exist in your organization. 在边缘传输服务器上,你所配置的任何组织限制都将应用到本地服务器。On Edge Transport servers, any organizational limits that you configure are applied to the local server.

注意Note:

组织限制也适用于外部发件人和外部收件人(匿名或未经身份验证的发件人或收件人):Organizational limits also apply to external senders and external recipients (anonymous or unauthenticated senders or recipients):

  • 对于来自外部发件人的入站邮件,Exchange 会将组织的最大发送邮件大小限制("收件人限制" 部分中所述的最大接收邮件大小限制应用于内部收件人)。For inbound messages from external senders, Exchange applies the organizational maximum send message size limit (the maximum receive message size limit as described in the Recipient limits section is applied to the internal recipient).

  • 对于向外部收件人的出站邮件,Exchange 会将组织的最大接收邮件大小限制("收件人限制" 部分中所述的最大发送邮件大小限制应用于内部发件人)。For outbound messages to external recipients, Exchange applies the organization maximum receive message size limit (the maximum send message size limit as described in the Recipient limits section is applied to the internal sender).

因此,邮件大小必须在发件人和收件人的邮件大小限制内。Therefore, a message size must be within the message size limits for both the sender and the recipient. 本主题后面的 "邮件大小限制的优先级和位置" 一节中也对此概念进行了说明。This concept is also explained in the Order of precedence and placement of message size limits section later in this topic.

大小限制Size limit 默认值Default value EAC 配置EAC configuration Exchange 命令行管理程序 配置Exchange Management Shell configuration
最大接收邮件大小Maximum size of a message received 可在 Excel Services 中打开的工作簿最大大小是 10 MB。10 MB 邮件流 > 接收连接器 > 多选项图标 > 组织传输设置 > 限制选项卡> 最大接收邮件大小(MB)Mail flow > Receive connectors > More options More Options icon > Organization transport settings > Limits tab > Maximum receive message size (MB) Cmdlet: Set-TransportConfigCmdlet: Set-TransportConfig
参数: MaxReceiveSizeParameter: MaxReceiveSize
最大发送邮件大小Maximum size of a message sent 10 MB10 MB 邮件流 > 接收连接器 > 多选项图标 > 组织传输设置 > 限制 > 最大发送邮件大小(MB)Mail flow > Receive connectors > More options More Options icon > Organization transport settings > Limits > Maximum send message size (MB) Cmdlet: Set-TransportConfigCmdlet: Set-TransportConfig
参数: MaxSendSizeParameter: MaxSendSize
邮件中的最大收件人数Maximum number of recipients in a message 500500 邮件流 > 接收连接器 > 多选项图标 > 组织传输设置 > 限制****最大收件人数Mail flow > Receive connectors > More options More Options icon > Organization transport settings > Limits Maximum number of recipients Cmdlet: Set-TransportConfigCmdlet: Set-TransportConfig
参数: MaxRecipientEnvelopeLimitParameter: MaxRecipientEnvelopeLimit
与邮件流规则的条件匹配的邮件的最大附件大小(也称为传输规则)Maximum attachment size for a message that matches the conditions of the mail flow rule (also known as a transport rule) 未配置Not configured
邮件流 > 规则 > 添加 > ](../media/ITPro_EAC_EditIcon.png) **** 添加图标 创建新规则,或选择现有规则,然后单击 "编辑编辑图标"。Mail flow > Rules > Add Add icon > Create a new rule, or select an existing rule, and then click Edit Edit icon.  单击" 更多选项"。Click More options.  如果> 任何附件 > 大小大于或等于,则使用条件应用此规则,并以 kb (kb)为单位输入值。Use the condition Apply this rule if > Any attachment > size is greater than or equal to, and enter a value in kilobytes (KB).|Cmdlet: New-TransportRule 、 Set-TransportRuleCmdlets: New-TransportRule, Set-TransportRule  参数: AttachmentSizeOverParameter: AttachmentSizeOver||与邮件流规则的条件相匹配的邮件的最大邮件大小Maximum message size for a message that matches the conditions of the mail flow rule|未配置Not configured|邮件流 > 规则 > 添加 > **** 添加图标 创建新规则,或选择现有规则,然后单击 "编辑编辑图标!["。Mail flow > Rules > Add Add icon > Create a new rule, or select an existing rule, and then click Edit Edit icon.
单击" 更多选项"。Click More options.
使用条件 以下情况下应用此规则> 邮件> 大小大于或等于,并以千字节 (KB) 为单位输入一个值。Use the condition Apply this rule if > The message > size is greater than or equal to, and enter a value in kilobytes (KB).
Cmdlet: New-TransportRuleSet-TransportRuleCmdlets: New-TransportRule, Set-TransportRule
参数: MessageSizeOverParameter: MessageSizeOver

若要查看这些组织限制的值,请在 Exchange 命令行管理程序 中运行以下命令:To see the values of these organizational limits, run the following commands in the Exchange Management Shell:

Get-TransportConfig | Format-List MaxReceiveSize,MaxSendSize,MaxRecipientEnvelopeLimit
Get-TransportRule | where {($_.MessageSizeOver -ne $null) -or ($_.AttachmentSizeOver -ne $null)} | Format-Table Name,MessageSizeOver,AttachmentSizeOver

连接器限制Connector limits

连接器限制应用于使用指定发送连接器、接收连接器、传递代理连接器或外部连接器传递邮件的所有邮件。Connector limits apply to any messages that use the specified Send connector, Receive connector, Delivery Agent connector, or Foreign connector for message delivery.

可以将特定邮件大小限制分配给组织中的 Active Directory 站点链接。邮箱服务器上的传输服务使用 Active Directory 站点和分配到 Active Directory IP 站点链接的成本作为确定组织中 Exchange 服务器之间成本最低的路由路径的因素之一。You can assign specific message size limits to the Active Directory site links in your organization. The Transport service on Mailbox servers uses Active Directory sites, and the costs that are assigned to the Active Directory IP site links as one of the factors to determine the least-cost routing path between Exchange servers in the organization.

可以将指定邮件大小限制分配给用于在组织中发送非 SMTP 邮件的传递代理连接器和外部连接器。You can assign specific message size limits to the Delivery Agent connectors and Foreign connectors that are used to send non-SMTP messages in your organization.

大小限制Size limit 默认值Default value EAC 配置EAC configuration Exchange 命令行管理程序 配置Exchange Management Shell configuration
通过接收连接器发送的邮件的最大大小Maximum size of a message sent through the Receive connector 36 MB36 MB 邮件流 > 接收连接器 > 编辑 编辑图标 > **** 常规> 最大接收邮件大小(MB)Mail flow > Receive connectors > Edit Edit icon > General > Maximum receive message size (MB) Cmdlet: New-ReceiveConnectorSet-ReceiveConnectorCmdlets: New-ReceiveConnector, Set-ReceiveConnector
参数: MaxMessageSizeParameter: MaxMessageSize
通过接收连接器发送的邮件中所有标题字段的最大大小Maximum size of all header fields in a message sent through the Receive connector 256 KB256 KB 不可用Not available Cmdlet: New-ReceiveConnectorSet-ReceiveConnectorCmdlets: New-ReceiveConnector, Set-ReceiveConnector
参数: MaxHeaderSizeParameter: MaxHeaderSize
通过接收连接器发送的邮件中收件人的最大数量Maximum number of recipients in a message sent through the Receive connector 邮箱服务器上的传输服务Transport service on Mailbox servers
默认_ <服务器>名称_:5000Default <ServerName>: 5000
客户端_ <代理>服务器名称_:200Client Proxy <ServerName>: 200
邮箱服务器上的前端传输服务Front End Transport service on Mailbox servers
默认前端_ <ServerName>:200Default Frontend <ServerName>: 200
出站代理 <前端>服务器名称_:200Outbound Proxy Frontend <ServerName>: 200
客户端_ <前端>服务器名称_:200Client Frontend <ServerName>: 200
如果来自匿名发件人的邮件中的收件人数目超出限制(例如,一个 Internet 发件人),则只接受前 200 个收件人的邮件。大多数邮件服务器将邮件传递给所有收件人之前,会在 200 个收件人的组中继续重新发送邮件。 If the number of recipients is exceeded in a message from an anonymous sender (for example, an Internet sender), the message is accepted for the first 200 recipients. Most messaging servers will continue to resend the message in groups of 200 recipients until the message is delivered to all recipients.
不可用Not available Cmdlet: New-ReceiveConnectorSet-ReceiveConnectorCmdlets: New-ReceiveConnector, Set-ReceiveConnector
参数: MaxRecipientsPerMessageParameter: MaxRecipientsPerMessage
通过发送连接器发送的邮件的最大大小Maximum size of a message sent through the Send connector 可在 Excel Services 中打开的工作簿最大大小是 10 MB。10 MB 邮件流 > 发送连接器 > 编辑 编辑图标 > 常规选项>卡最大发送邮件大小(MB)Mail flow > Send connectors > Edit Edit icon > General tab > Maximum send message size (MB) Cmdlet: New-SendConnectorSet-SendConnectorCmdlets: New-SendConnector, Set-SendConnector
参数: MaxMessageSizeParameter: MaxMessageSize
通过 Active Directory 站点链接发送的邮件的最大大小Maximum size of a message sent through the Active Directory site link 无限制Unlimited 不可用Not available Cmdlet: Set-AdSiteLinkCmdlet: Set-AdSiteLink
参数: MaxMessageSizeParameter: MaxMessageSize
通过传递代理连接器发送的邮件的最大大小Maximum size of a message sent through the Delivery Agent connector 无限制Unlimited 不可用Not available Cmdlet: New-DeliveryAgentConnectorSet-DeliveryAgentConnectorCmdlets: New-DeliveryAgentConnector, Set-DeliveryAgentConnector
参数: MaxMessageSizeParameter: MaxMessageSize
通过外部连接器发送的邮件的最大大小Maximum size of a message sent through the Foreign connector 无限制Unlimited 不可用Not available Cmdlet: Set-ForeignConnectorCmdlet: Set-ForeignConnector
参数: MaxMessageSizeParameter: MaxMessageSize

若要查看这些连接器限制的值,请在 Exchange 命令行管理程序 中运行以下命令:To see the values of these connector limits, run the following command in the Exchange Management Shell:

Get-ReceiveConnector | Format-Table Name,Max*Size,MaxRecipientsPerMessage; Get-SendConnector | Format-Table Name,MaxMessageSize; Get-AdSiteLink | Format-Table Name,MaxMessageSize; Get-DeliveryAgentConnector | Format-Table Name,MaxMessageSize; Get-ForeignConnector | Format-Table Name,MaxMessageSize

服务器限制Server limits

服务器限制应用于特定邮箱服务器或边缘传输服务器。可以在每台邮箱服务器或边缘传输服务器上单独设置邮件大小限制。Server limits apply to specific Mailbox servers or Edge Transport servers. You can set these message size limits independently on each Mailbox server or Edge Transport server.

大小限制Size limit 默认值Default value EAC 配置EAC configuration Exchange 命令行管理程序 配置Exchange Management Shell configuration
通过 Web 上的 Outlook 客户端发送的邮件的最大大小Maximum size for a message sent by Outlook on the web clients 35 MB35 MB 不可用Not available 可以在邮箱服务器上的 web.config XML 应用程序配置文件中配置此值。有关详细信息,请参阅 配置客户端特定的邮件大小限制You configure this value in web.config XML application configuration files on the Mailbox server. For more information, see Configure client-specific message size limits.
通过 Exchange ActiveSync 客户端发送的邮件的最大大小Maximum size for a message sent by Exchange ActiveSync clients 10 MB10 MB 不可用Not available 可以在邮箱服务器上的 web.config XML 应用程序配置文件中配置此值。有关详细信息,请参阅 配置客户端特定的邮件大小限制You configure this value in web.config XML application configuration files on the Mailbox server. For more information, see Configure client-specific message size limits.
通过 Exchange Web 服务 客户端发送的邮件的最大大小Maximum size for a message sent by Exchange Web Services clients 64 MB64 MB 不可用Not available 可以在邮箱服务器上的 web.config XML 应用程序配置文件中配置此值。有关详细信息,请参阅 配置客户端特定的邮件大小限制You configure this value in web.config XML application configuration files on the Mailbox server. For more information, see Configure client-specific message size limits.

边缘传输服务器和邮箱服务器上可用的拾取目录也具有可配置的邮件大小限制。The pickup directory that's available on Edge Transport servers and Mailbox servers also has messages size limits that you can configure. 通常,拾取目录不用于日常邮件流。Typically, the pickup directory isn't used in everyday mail flow. 它由管理员用来测试邮件流,或由需要创建并提交各自的邮件文件的应用程序使用。It's is used by administrators for mail flow testing, or by applications that need to create and submit their own messages files. 有关详细信息,请参阅配置分拣目录和重播目录For more information, see Configure the Pickup Directory and the Replay Directory.

  • 置于拾取目录中的邮件文件中所有标题字段的最大大小:64 KB。Maximum size of all header fields in a message file placed in the pickup directory: 64 KB.

  • 置于拾取目录中的邮件文件中收件人的最大数目:100。Maximum number of recipients in a message file placed in the pickup directory: 100.

收件人限制Recipient limits

收件人限制应用于特定用户对象,例如邮箱、邮件联系人、邮件用户、通讯组或启用邮件的公用文件夹。Recipient limits apply to a specific user object, such as a mailbox, mail contact, mail user, distribution group, or a mail-enabled public folder.

大小限制Size Limit 默认值Default value EAC 配置EAC configuration Exchange 命令行管理程序 配置Exchange Management Shell configuration
可以发送给特定收件人的邮件的最大大小Maximum size of a message that can be sent to the specific recipient 网站邮箱设置策略:36 MBSite mailbox provisioning policies: 36 MB
所有其他收件人类型:不限All other recipient types: unlimited
对于邮箱:For mailboxes:
收件人 > 邮箱](../media/ITPro_EAC_EditIcon.png) > > > **** **** > **** > **** **** **** 编辑编辑图标>邮箱功能 "邮件流" 部分 "邮件大小限制" 部分视图详细信息接收的邮件部分最大邮件大小(KB) > Recipients > Mailboxes > Edit Edit icon > Mailbox features > Mail flow section > Message size restrictions section > View details > Received messages section > Maximum message size (KB)  对于邮件用户:For mail users:  收件人 > 联系人 > > > **** > **** > **** **** **** **** 编辑编辑图标邮件流设置邮件大小限制查看详细信息接收的邮件部分最大邮件大小(KB)  >Recipients > Contacts > Edit Edit icon > Mail flow settings > Message size restrictions > View details > Received messages section > Maximum message size (KB)  对于其他类型的收件人,此设置在 EAC 中可用。This setting available in the EAC for other types of recipients.|Cmdlet:Cmdlets:  New-distributiongroupSet-DistributionGroup  Get-dynamicdistributiongroupSet-DynamicDistributionGroup  Set-MailboxSet-Mailbox  Enable-mailcontactSet-MailContact  MailUserSet-MailUser  Enable-mailpublicfolderSet-MailPublicFolder  新 New-sitemailboxprovisioningpolicyNew-SiteMailboxProvisioningPolicy  New-sitemailboxprovisioningpolicySet-SiteMailboxProvisioningPolicy  参数: MaxReceiveSizeParameter: MaxReceiveSize||可以由特定发件人发送的邮件的最大大小Maximum size of a message that can be sent by the specific sender|无限制Unlimited|对于邮箱:For mailboxes:  收件人 > 邮箱 > > > **** **** > **** > **** **** **** 编辑编辑图标>邮箱功能 "邮件流" 部分 "邮件大小限制" 部分视图详细信息发送的邮件部分最大邮件大小(KB) > Recipients > Mailboxes > Edit Edit icon > Mailbox features > Mail flow section > Message size restrictions section > View details > Sent messages section > Maximum message size (KB)  对于邮件用户:For mail users:  收件人 > 联系人 > **** > > **** > **** > **** **** 编辑编辑图标 "邮件流设置" "邮件大小限制" 部分查看详细信息发送的邮件部分最大邮件大小(KB) > Recipients > Contacts > Edit Edit icon > Mail flow settings > Message size restrictions section > View details > Sent messages section > Maximum message size (KB)  对于其他类型的发件人,此设置在 EAC 中可用。This setting available in the EAC for other types of senders.|Cmdlet:Cmdlets:  New-distributiongroupSet-DistributionGroup  Get-dynamicdistributiongroupSet-DynamicDistributionGroup  Set-MailboxSet-Mailbox  Enable-mailcontactSet-MailContact  MailUserSet-MailUser  Enable-mailpublicfolderSet-MailPublicFolder  参数: MaxSendSizeParameter: MaxSendSize||由特定发件人发送的邮件中收件人的最大数目Maximum number of recipients in a message that's sent by the specific sender|无限制Unlimited|对于邮箱:For mailboxes:  收件人 > 邮箱 > > > **** > **** > **** **** **** **** 编辑编辑图标邮箱功能 "邮件流" 部分视图详细信息收件人限制部分最大收件人数![ >Recipients > Mailboxes > Edit Edit icon > Mailbox features > Mail flow section > View details > Recipient limit section > Maximum recipients
对于邮件用户,此设置在 EAC 中不可用。This setting isn't available in the EAC for mail users.
Cmdlet:Cmdlets:
Set-MailboxSet-MailUserSet-Mailbox, Set-MailUser
参数: RecipientLimitsParameter: RecipientLimits

若要查看这些限制的值,请运行 Exchange 命令行管理程序 中收件人类型相应的 Get- cmdlet。To see the values of these limits, run the corresponding Get- cmdlet for the recipient type in the Exchange Management Shell.

例如,若要查看在特定邮箱上配置的限制,请运行以下命令:For example, to see the limits that are configured on a specific mailbox, run the following command:

Get-Mailbox <MailboxIdentity> | Format-List MaxReceiveSize,MaxSendSize,RecipientLimits

若要查看在所有用户邮箱上配置的限制,请运行以下命令:To see the limits that are configured on all user mailboxes, run the following command:

$mb= Get-Mailbox -ResultSize unlimited; $mb | where {$_.RecipientTypeDetails -eq 'UserMailbox'} | Format-Table Name,MaxReceiveSize,MaxSendSize,RecipientLimits

邮件大小限制的优先级顺序和位置Order of precedence and placement of message size limits

邮件大小限制的优先级顺序是强制实施的最严格的限制。唯一的问题是在哪里强制实施该限制。我们的目标是尽可能早地在传输管道中拒绝过大邮件。例如,如果组织限制较低,那么让 Internet 接收连接器接受最终被拒绝的过大邮件会造成系统资源的浪费。配置组织、服务器和连接器限制时,务必要最大限度地减少任何不必要的邮件处理。通过使所有位置中的限制保持一致,或针对邮件进入 Exchange 组织的位置配置更严格的限制来执行此操作。The order of precedence for message size limits is the most restrictive limit is enforced. The only question is where that limit is enforced. The goal is to reject messages that are too large as early in the transport pipeline as possible. For example, it's a waste of system resources for the Internet Receive connector to accept large messages that are eventually rejected because of a lower organizational limit. Make sure that your organization, server, and connector limits are configured in a way that minimizes any unnecessary processing of messages. You do this by keeping the limits the same in all locations, or by configuring more restrictive limits where messages enter your Exchange organization.

邮件流规则中的邮箱和邮件大小限制的邮件大小限制是对顺序的例外。An exception to the order is message size limits on mailboxes and messages size limits in mail flow rules. 在邮件流规则处理邮件之前,Exchange 会检查邮箱允许的最大邮件大小。Exchange checks the maximum message size that's allowed on mailboxes before mail flow rules process messages. 例如,组织的邮件大小限制为 50 MB,你在邮箱上配置的是 35 MB 限制,并且配置了邮件流规则来查找并拒绝大于 40 MB 的邮件。For example, your organization's message size limit is 50 MB, you configure a 35 MB limit on a mailbox, and you configure a mail flow rule to find and reject messages larger than 40 MB. 如果外部发件人向邮箱发送 45 MB 的邮件,在邮件流规则评估该邮件之前该邮件已被拒收。If an external sender sends a 45 MB message to the mailbox, the message is rejected before the mail flow rule is able to evaluate the message.

经过身份验证的发件人和收件人(通常为内部邮件发件人和收件人)之间的收件人限制不受组织邮件大小的限制。因此,可以配置特定发件人和收件人超出组织的默认邮件大小限制。例如,可以允许特定邮箱发送和接收比组织的其他邮箱大的邮件,方法是为这些邮箱配置自定义发送和接收限制。Recipient limits between authenticated senders and recipients (typically, internal message senders and recipients) are exempt from the organizational message size restrictions. Therefore, you can configure specific senders and recipients to exceed the default message size limits for your organization. For example, you can allow specific mailboxes to send and receive larger messages than the rest of the organization by configuring custom send and receive limits for those mailboxes.

然而,该例外仅适用于经身份验证的发件人和收件人(通常为内部发件人和收件人)之间发送的邮件。对于匿名发件人和收件人(通常为 Internet 发件人或 Internet 收件人)之间发送的邮件,则应用组织限制。例如,假设组织邮件大小限制为 10 MB,但你为营销部门的用户配置的发送和接收邮件高达 50 MB。这些用户能够彼此交换大型邮件,但不能与 Internet 发件人和收件人(未经身份验证的发件人和收件人)交换邮件。However, this exemption applies only to messages sent between authenticated senders and recipients (typically, internal senders and recipients). For messages sent between anonymous senders and recipients (typically, Internet senders or Internet recipients), the organizational limits apply. For example, suppose your organizational message size limit is 10 MB, but you configured the users in your marketing department to send and receive messages up to 50 MB. These users will be able to exchange large messages with each other, but not with Internet senders and recipients (unauthenticated senders and recipients).

免受大小限制的邮件Messages exempt from size limits

以下列表显示了由邮箱服务器或边缘传输服务器生成的邮件类型,除了邮件中允许的最大收件人数目的组织限制,这些邮件免除了所有邮件大小限制:The following list shows the types of messages that are generated by Mailbox servers or Edge Transport servers that are exempted from all message size limits except the organizational limit for the maximum number of recipients that are allowed in a message:

  • 系统邮件System messages

  • 代理生成的邮件Agent-generated message

  • 传递状态通知 (DSN) 邮件(亦称为"未送达报告"、"NDR"或"退回邮件")。Delivery status notification (DSN) messages (also known as non-delivery reports, NDRs, or bounce messages). 但是,可以使用set-transportconfig cmdlet 上的_ExternalDsnMaxMessageAttachSize_和_InternalDsnMaxMessageAttachSize_参数来限制 dsn 邮件中包含的原始邮件的大小(因此,dsn 邮件本身的有效大小)。However, you can use the ExternalDsnMaxMessageAttachSize and InternalDsnMaxMessageAttachSize parameters on the Set-TransportConfig cmdlet to limit the size of original messages that are included in DSN messages (hence, the effective size of the DSN message itself).

  • 日记报告邮件Journal report messages

  • 被隔离的邮件Quarantined messages