>>>>> Austin Frank wrote:

> Debugger entered--Lisp error: (wrong-type-argument stringp nil)
>   string-match(nil "\"John Q. Public\" <jqpublic@MIT.EDU>")
>   nnmail-fancy-expiry-target("mail.academic")

You may possibly be the first person who tried using `to-from'
and `nnmail-fancy-expiry-target' ever since it was introduced in
December, 2001.  IIUC, this is a bug that arises in the case
where `message-dont-reply-to-names' is nil, though it is likely
to default to nil in most Gnus users.  Could you try this patch?