FWIW, this is what I have on trailing colons:

>
>Date sent:      Fri, 14 Jul 2000 18:03:30 -0400 (EDT)
>From:           [log in to unmask]
>To:             [log in to unmask]
>Subject:        Re: (Fwd) Problem processing mail file from [log in to unmask]
>
>Actually, I think Grant just spotted an even better one.  In the
>canned message that goes out when subscriptions have expired, as
>defined in default.mailtpl, we find:
>
>  >>> RENEW2 Expiration of your subscription to the &LISTNAME list
>  .re owners
>  &WEEKDAY, &DATE &TIME
>
>  Your subscription to the &LISTNAME list has expired and you have failed
>  to confirm it in the &DELAY day delay that you had been granted. You
>  have therefore been automatically removed from the list. You can
>  re-subscribe to the list, if you want to, by sending the following
>  command to &MYNAMES:
>
>  .ce SUBscribe &LISTNAME
>
>We've had a couple who got error messages about the "To:" address
>having a colon after it, ie "[log in to unmask]: "  I still
>don't know why the aol'ers were getting quotes in there;  flaky as AOL
>is, it's probably something to do with their software.  But the colon
>seems to be a problem, too.
>
>For our lists, I'm customizing RENEW1 and RENEW2, anyway, so I'm
>adding a space between &MYNAMES and the colon.  (Also deleteing the
>".re owners" since we've had several dozen send the subscribe command
>via reply.  No one has actually written anything that looked like it
>was intended for a listowner, so I suspect it'll work better for us
>if replies go to the server.)  Perhaps the colon issue needs to be
>changed in default.mailtpl, too?
>