2.2.14 [RFC1939] Section 7, UIDL Command

V0007:

The specification states: "Arguments: a message-number (optional), which, if present, may NOT refer to a message marked as deleted."

Microsoft Office Outlook 2007, Microsoft Outlook 2010, Microsoft Outlook 2013, Microsoft Outlook 2016, Microsoft Outlook 2019

The client MAY send an argument.

Outlook never sends the UIDL command with an argument.

C0035:

The specification states: "Restrictions: may only be given in the TRANSACTION state."

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

The client SHOULD only send the UIDL command when in the TRANSACTION state.

C0036:

The specification states: "Discussion: If an argument was given and the POP3 server issues a positive response with a line containing information for that message."

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

If the UIDL command includes an argument and the server is returning success, then it MUST issue a positive response line (a "unique-id listing").

This statement has no impact as Outlook never sends the UIDL command with an argument.

C0037:

The specification states: "If no argument was given and the POP3 server issues a positive response, then the response given is multi-line. After the initial +OK, for each message in the maildrop, the POP3 server responds with a line containing information for that message."

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

If the UIDL command does not include an argument and the server is returning a positive response, then the server MUST issue a multi-line response. The initial line MUST be the positive response "+OK". Then the server MUST send a "unique-id list" for each message in the maildrop on its own line.

C0038:

The specification states: "In order to simplify parsing, all POP3 servers are required to use a certain format for unique-id listings. A unique-id listing consists of the message-number of the message, followed by a single space and the unique-id of the message in octets."

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

The unique-id listing MUST consist of the number of the message followed by one or more space or tab characters, and then the unique-id of the message in octets. The server MAY follow this with additional information.

C0039:

The specification states: "The unique-id of a message is an arbitrary server-determined string, consisting of one to 70 characters in the range 0x21 to 0x7E, which uniquely identifies a message within a maildrop and which persists across sessions."

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

The unique-id MUST consist of one to 70 characters in the range 0x2e to 0x7E. The server MUST persist the unique-id that identifies the message across sessions.

C0040:

The specification states: "The server should never reuse a unique-id in a given maildrop, for as long as the entity using the unique-id exists."

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

The server SHOULD NOT reuse a unique-id for as long as the entity using the unique-id exists. If the server violates this statement, then the action expected on one message could be performed unexpectedly on another message with the same unique-id.

C0041:

The specification states: "Clients should be able to handle a situation where two identical copies of a message in a maildrop have the same unique-id."

Office Outlook 2007, Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019

The client SHOULD be able to handle two identical copies of a message having the same unique-id.

Outlook does not fully comply with the use of SHOULD in the statement. Using Outlook, an action specified by the user on one message can happen on either message with the identical unique-id during synchronization. But, since the messages are identical, this has little impact. For example, if a user marks one message header for download, then Outlook can download the other message header instead.