Email Sending via TLS

[iscon]

Also two cases (one being my own): Although the SMTP provider uses TLS and port 587 and sending works well with TB it doesn't work in Espo. If I switch to no encryption and port 25 Espo is doing the job. With other clients it works as it should. On the same instance sending via 587 works without problems when using Gmail for instance.
Any idea?