Q: How can I ensure that I receive copies of my own messages posted to a list?

By Ben Parker
Chief Corporate Consultant, L-Soft

For some time, LISTSERV list subscribers using Gmail (or other addresses served by Google) have complained about not receiving copies of their own messages posted to a list. Users of Microsoft's Exchange/Outlook, Outlook.com (and variants), and Office 365 have experienced the same issues. Many people like to receive copies of their own postings as "proof" that their messages have been successfully posted to the list and distributed to other subscribers.

Another similar issue occurs in academic and corporate environments where people post an identical message to multiple lists but only receive back one copy (sometimes none). How can they know that the message has been distributed successfully to all of the expected lists?

If the subscriber has REPRO set in their LISTSERV subscriber options for the lists in question, LISTSERV will send back a copy of the message to the sender. However, the reason that the "sent back" message is not seen is because the subscriber's mail system, in an effort to prevent clutter by duplicate emails, sees that the message is the same as a message that was previously composed and sent. The mail system can do this because all mail systems create a (normally hidden) field in the headers of the message when it's composed and sent. This field is named Message-ID and contains a unique identifying string.

Here is an example from Gmail:

Normally, this field is not modified when the message passes through LISTSERV processing, so it will be the same in the outgoing messages distributed to the list subscribers. It's this Message-ID field that is compared between the incoming message and previously sent messages. If there is a match, the incoming email is discarded, and the user never sees it.

In the past, the only way to overcome this was for affected users to set their LISTSERV subscriber options to ACK. Then LISTSERV sends a separate message to the user when their message posts:

This acknowledgement message will have a unique and different Message-ID, which will not match any previous IDs in your "sent" folder, so you will see this message.

The ACK option described above is still available, but new in the LISTSERV 16.0-2017a level-set build is a new setting for dealing with this issue. This option can be set sitewide by server administrators or at the list level by list owners. Simply add this line in the List Header/List Configuration:

This new option forces LISTSERV to change the Message-ID field when it processes the message for posting to the list. This is an example of a changed header:

Now, because the Message-ID field does not match the one in the previously sent message, both the original sent message and the sent-back copy will both appear in your Gmail mailbox.

References

LISTSERV 16.0-2017a Level-Set What's New Manual
http://www.lsoft.com/manuals/16.0/LISTSERV16.0-2017a_WhatsNew.pdf

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