Most institutions of Higher Education have email forwarding services e.g,
[log in to unmask] is not a mail repository but a forwarding agent.
Since I've been using that address, I have moved mail systems within PSU
about 4 times.   No one but me cared.  Why? because I updated our
@PSU.EDU mail forwarding system to point to my then-current mail server.

Of course I needed a mail client and supporting infrastructure that
allowed me to generate a consistent FROM: field regardless of where I
read my mail or from where I sent it.

Lacking that, then LISTSERV(R) requires multiple subscription addresses
(if the list is SEND= PRIVATE (or equivalent).  Of course not all of
those addresses would need to RECEIVE postings ie., SET listname NOMAIL.

Other M.L.M. have expression-matching.  Of course though it is not always
true that [log in to unmask] is the same as [log in to unmask]

YMMV.

/Pete Weiss