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What does it mean when a message is held with the reason "Message has implicit destination"?

An 'implicit destination' alert is sent both to the poster of the original message and to the mailing list's moderator.  There are three possible causes:

  1. It could mean that a message has been posted to your mailing list and Bcc'd (Blind Carbon Copied) to one or more other addresses or mailing lists.  It's the Bcc'd address that you'll get the warning about.   This is an anti-spamming feature of Mailman, because a common ploy amongst spammers is to post messages to many different addresses by means of Bcc. The Subject line of the message will normally show (in square brackets) the mailing list name that was the main recipient of the message.
    As list moderator, you will need to open the link provided and either approve, discard or reject the message that has been held.

    If (as list moderator) you would prefer not to have to vet such messages, you can set your list to accept them automatically:   Go to the Privacy Options page and then Recipient Filters.   The first option on this page reads "Must posts have list named in destination (to, cc) field (or be among the acceptable alias names, specified below)?".  Set this option to No, and then click 'Submit Your Changes' button.   However, bear in mind that this could render your list more vulnerable to spam.

  2. Another possibility is if the list acts as an 'umbrella list' for another mailing list; that is,  one of its 'members' is the address of another mailing list.   What happens is that the member list receives the message that had originally been sent to its host 'umbrella' list, but the umbrella list's name is shown in the address box, not the member list.   To prevent such messages being held, you need to declare the umbrella list's address as an "acceptable alias" of the member list.
    For example, suppose a mailing list called toplist contains another mailing list called sublist as a 'member'.   The administrator of sublist needs to open the Recipient Filters page, which is in the Privacy Options section of sublist's admin page.   Within this section, there's an option labelled "Alias names (regexps) which qualify as explicit to or cc destination names for this list".  In the box alongside, enter           (toplist being the name of the host umbrella list)

    and then click 'Submit Your Changes' button.

    This does not work retrospectively, so for any messages that have been held, the list's administrator will need to open the Tend to pending moderator requests link in the list's admin page, and either approve or reject the message that has been held.

  3. A third possibility is that the mailing list has been emailed using the shortened form of Sussex's email domain name (, for example   Although the mail system recognises this and delivers the message to Mailman, Mailman will not recognise the shortened form, and will hold the message for approval.   A solution would be to include the shortened form as an alias for the mailing list, as described in item 2 above.  However, this scenario is normally very rare, so it may not be worth it.

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This is question number 1190, which appears in the following categories:

Created by Andy Clews on 17 October 2005 and last updated by Richard Byrom-Colburn on 29 September 2016