>address looks fishy; but OTOH mail seem to have gone through earlier. Is
>[log in to unmask] a valid address or not?
 
If that is actually how it appears in the subscribe list,
then it should definitely be deleted.  It is not a valid
hostname by any stretch of the imagination.
 
If in fact it does not appear as such in your subscriber
list, then I suspect either one of two things: user has an
incorrect forward setup at their mail host, or a mail
transfer agent did some re-writing and did so incorrectly.
 
/P