Ticket Creation Failed

I have a problem with just 2 users within my organisation. Whenever either
send an e-mail to any RT queue they always get a "Ticket Creation Failed"
message back with no other info.

Both users are priviledged and are allowed to access WebRT. One user was
created through the WebUI and the other was originally auto-created. All the
queues they try to create tickets in have “Everyone” set with “create
ticket” rights.

I “inherited” this sytem so I don’t know when these users stopped being able
to submit tickets by e-mail.

RT version is 3.0.7 running on FreeBSD 5.2.1