LISTSERV changes the headers of messages it distributes in various ways, generally to make it easier for recipients to recognize them and filter them appropriately, and (in some cases) to prevent some problematic situations. For instance, if 'Cc:'s are included in messages distributed to a mailing list, and ability to post messages to that mailing list are restricted, then the cc:ed addresses could end up getting involved in a conversation that they can neither leave nor participate in.

With that said, there is a subscription option called IETFHDR which, among other things, tells LISTSERV to not make this sort of change to the headers of messages it distributes to the subscriber; so if individual subscribers, prefer, they can switch to this subscription option.  This can be done from the subscription page of the mailing list (linked to from the right side of the mailing list's archive page).  The option they want is next to 'mail header style' and is labeled 'sendmail-style [IETFHDR]'.

Note that this affects how they see mail they receive through the mailing list.  It doesn't affect how others will see any messages they post to the mailing list.

In some cases, it might make sense for all of a particular mailing list's subscribers to be set to IETFHDR.  To make all subscribers have this subscription option, you can set:

Default-Options= IETFHdr

in the mailing list's configuration (so that any new subscribers have the IETFHDR option set) and issue a

quiet set listname ietfhdr for *@*"

command to LISTSERV (for instance by going under 'List Management' to 'LISTSERV Command') so that all existing subscribers will have that subscription option set.

IETFHDR does have some side-effects that you should be aware of:

    • With IETFHDR, the mail headers cannot be changed in any way by LISTSERV. If someone sends mail to LisTnAmE@lIstserV.HoSt.CoM, that capitalization is exactly what people on the receiving end will see if their subscription is set to IETFHDR.
    • If you have Reply-To= coded in your list header, that will not be respected for subscriptions set to IETFHDR.
    • Messages posted to the mailing list will have a 'Sender:' header pointing to the owner-NAMEOFLIST@... address, and this cannot be disabled.  (This was one of the requirements of the proposed standard that IETFHDR is based on.)
    • A subscription cannot be set to SUBJECTHDR and IETFHDR at the same time. However, you can add

      Misc-Options= IETFHDR_SUBJECT_TAG

      to a mailing list's configuration to cause the subject tag to be added to the subject of messages sent to subscribers with the IETFHDR set, causing IETFHDR to function similarly to SUBJECTHDR in that way.