We use an external email-server from our domain hoster.
ETRN or multi-drop settings
For ETRN or multi-drop, specify the hostname or IP address of your secondary mail server. (If using the standard e-mail setup, this field can be left blank.)
Secondary mail server: pop3.xxx.de
SMTP server
The server can deliver outgoing messages directly to their destination (recommended in most cases) or can deliver them via your Internet provider's SMTP server (recommended if you have an unreliable Internet connection or are using a residential Internet service). If using your Internet provider's SMTP server, specify its hostname or IP address below. Otherwise leave this field blank.
Address of Internet provider's mail server: smtp.xxx.de
In standard config port 25 and 110 are used. The SSL/TLS ports are 995 and 465.
I stumbled over this:
Internet provider's outgoing port 25 is blocked: How to set an alternative outgoing port for the SMTP server
If your Internet provider is blocking outgoing smtp port 25 on your internet connection but your provider is offering an alternative outgoing port (or when using some relay service) you can simply set this alternative port by adding it to the 'Address of Internet provider's mail server' value in the 'E-mail delivery settings' screen of the server-manager like this:
<internet providers mail server name or ip-address>:<alternative port>
For example: mail.mydomain.com:587
This setting does not alter the incoming smtp mail server port on SME server, which will still use port 25. Refer to a workaround in
http://wiki.contribs.org/PortRedirectDoes this mean, a port-redirect from 25-->465 and 110 --> 965 will do it?
Thank's for any reply/hint.
stefan
Edit:
In the meanwhile I found this in an old thread:
https://forums.contribs.org/index.php?topic=44971.0Leaves still the question for the 110 --> 965 port.