Asai:
> Greetings,
>
> We are getting reports, more and more, of email clients (Type App, Mac
> Mail, iOS Mail) that seem to send email, and show that the email has
> been sent on the client, but the mail server has no record of email ever
> reaching the SMTP service, nor does it even seem that the client is
> connecting to the server.
This means that client systems are compromised with malware
that sends email directly to the outside world, bypassing
your mail server.
To stop these, block outbound port 25 on your firewall for all
systems except your mail server.
Wietse
