Special characters in email addresses

[Bjorn Swift]

Dear listmembers.

Some of my users tend to put (by accident I assume) invalid characters in
the email address field, such as áéýúíóþæðö. What seems to happen is that
the message is sent to postmaster, without any error going to the sender.

First I though this was an MTA problem, but my PHP test script could send a
message to æðö@example.com no problem. While my maillogs show the test
script's attempt to deliver æðö@example.com, the logs from IMP's attempt are
identical to what is produced it I send an email directly to
postmaster@mydomain.com (that is, it looks as if IMP sends the email
directly to postmaster without trying to send it to æðö@example.com).

So I guess my questions are these:
What kind of checks are there made to the recipient address before a message
is sent? Could IMP in any possible way, replace the recipient with the
postmaster address if the email address is invalid ? (( How is email sent in
IMP, though PEAR ? Could that be interfearing ?))

Should I perhaps be looking in the other direction, the MTA direction ? ;)

Perhaps someone using the same software I am try this out and see what
results they get?
   Horde Framework: RELENG_2 - dl Jan 25th
   IMP:             RELENG_3 - dl Jan 25th
   MTA:             Postfix 20010228

Thanks,
Björn Swift