Lost connection with mail.xxx.de [xxx.xxx.xxx.xxx] while sending message body / MTP incoming data timeout - closing connection. (in reply to end of DATA command) / conversation with mail.xxx.com[xxx.xxx.xxx.xxx] timed out while sending message body

Hi

We are experiencing various timeout problems after installing the Sophos E-Mail Appliance.

The installation occured this Monday, by Wednesday we had 36 e-mails in our queue all with similar error notifications, i.e.:

- Lost connection with mail.xxx.de [xxx.xxx.xxx.xxx] while sending message body
- MTP incoming data timeout - closing connection. (in reply to end of DATA command)
- conversation with mail.xxx.com[xxx.xxx.xxx.xxx] timed out while sending message body
- conversation with mail.xxx.com[xxx.xxx.xxx.xxx] timed out while sending end of data

This problem only occurs with certain domains/e-mail addresses. Many, but not all of them have some kind of SMTP problem which was checked via mxtoolbox.com, e.g.

- SMTP failed to connect
- SMTP Transaction Time: Not good! on Transaction Time

As said though, some of the domains we want to wrote e-mails to apparently do not have any problems via mxtolbox.com.

When checking our own domain, we receive the info that
"SMTP Banner Check - Reverse DNS does not match SMTP Banner" and
"SMTP Transaction Time - 6.203 seconds - Warning on Transaction Time".

We have now stopped the e-mail appliance and are sending out mails as before the implementation as no problems occured here.
We want to use the e-mail appliance but cannot at the moment as we do not know why so many e-mails are staying in the queue with the status "Delivery deffered".
Can anyone help?

Thank you in advance
Mark
mm@wefra.de
admin@wefra.de