Hello
Since a while we support SSL and TLS on our server. Recently i spotted a strange issue, that my server connected with the SSL host instead of the TLS host.

I had the idea, that SmarterMail uses the hostname added in the configuration of a domain to send mails.
Of course, this is wrong and i really didn't think much :-)

SmarterMail uses the setting in Settings -> Protocols -> SMTP Out -> Outbound IPv4 which is the primary IP per default. In my case, this is the IP address of the SSL host. This explains why the outgoing connection for TLS hosts was wrong. We had a luck, that receiving mail servers didn't bounce the mails at all. Only few mail servers bounced such mails. 

I had to change the setting in SMTP out to Use the Domain's IP. Then i had to change the Outbound IPv4 for each domain to the desired ip address. To simply this i used the Domain Defaults by propagating the right ip address to the existing domains.

Hopeful this posts helps other people and i hope, that this the simplest and correct solution. 

Silly me :-)

Cheers!