So, what was wrong ?

send mail for projects or tickets, only works on ssl mode. so the configuration depend on web container, and the Path directory.
:whistle:

only works on ssl mode

Not so sure.
I just think your inital smtp server has some typical restriction.
Trying another one solves the issue, but not because of ssl, just because of other smpt server.
I use a smtp server in no ssl mode without any issue since several years with Project'Or RIA with no issue, and so do many community members.