Since last week, or the most recent upgrade of xeams, it would appear that inbound messages are not being authenticated before being sent to the outbound message queue.  I started to get messages that my outbound message queue contained 200, then 500 and then over 1000 messages all about 1KB being stuck in the outbound queue.  Removing them physically from the file folder was OK but I have set the server as being a closed relay only to allow authenticated relaying from my users of a particular domain.

I am using the community version, and this has been ideal for over three years - so why has this just started to happen.  It would appear also that many of these messages are being generated outside of the UK and I have blacklisted those countries.

The following is an FYI for other readers.

After posting this message on the forum, Ivor contacted our technical support via email. It was determined that someone on the Internet had cracked a user id/password belonging to one of the users and was now misusing it to relay messages. The problem was fixed after resetting the password.