After some time testing other ports and different names for the SMTP Server, I landed on port 587 which worked and I was able to send secure SSL/TLS mails.
Strangely, the settings for the mail client says the SMTP port should be 465 but I guess there's some bug there. I will wait for my client to get back to me about that and if I get the port 465 working, I'll update this answer. Otherwise, I'll just continue with port 587.
Kind regards,
Meri