Can't connect to SMTP from WordPress, WHMCS or other software.

Hi, I have this weird issue. I can't seem to connect to SMTP from WHMCS, or WordPress (for example) to send an email. It's just not connecting. All settings are correct. Port for SSL, correct. Is there any setting in exim I should be aware of that could cause this? I've tried disabling stuff like "Prevent user nobody from sending mail", the SMTP delay, weak ciphers etc. literally nothing works and cPanel Support have been more than useless. Anybody got any suggestions? Thanks