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Epictetus-6184 asked joyceshen-MSFT commented

X-MS-Exchange-Organization-OriginalEnvelopeRecipients header values always encoded

Is there any MS exchange server that would by default encode the values for X-MS-Exchange-Organization-OriginalEnvelopeRecipients: as shown below. Or is it encoded by Office365 applications

X-MS-Exchange-Organization-OriginalEnvelopeRecipients: =?us-ascii?Q?;jbyv@iai?=

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Hi @Epictetus-6184

Could you please provide more information about your environment? Are you using on-premise Exchange or Exchange online? What's the sender and recipients for this message? Generally the value is added by the creator of the message. And according to my research, seems the value like =?us-ascii? is common in message header, like this.

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thanks for your reply;
It is an on-Premises exchange. The sender and recipient are both Microsoft outlook. I have found an example where X-MS-Exchange-Organization-OriginalEnvelopeRecipients: is not encoded, hence wondering if the encoding of the header values is based on exchange server configuration?

In the link below, when TrustedMailOutboundEnabled is set to true; we can expect to see these headers. However, it is not clear if the values are encoded by default?

 The TrustedMailOutboundEnabled parameter specifies whether messages sent to recipients in the remote domain are treated as trusted messages. Valid values are:
 $true: Outbound messages to recipients in the remote domain are considered safe and will bypass content filtering and recipient filtering. We recommend that you use this value in cross-forest deployments.
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According to my search,,care%20and%20feeding


A mail composing program claiming compliance with this specification
MUST ensure that any string of printable ASCII characters in a
message header that begins with "=?" and ends with "?=" be a valid

A mail reading program claiming compliance with this specification
must be able to distinguish encoded-words from "text", "ctext", or
"word"s anytime they appear in appropriate places in message headers.
The program must be able to display unencoded text if the character
set is "US-ASCII". For the ISO-8859-* character sets, the mail
reading program must at least be able to display the characters which
are also in the ASCII set.

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