Hello there. I recently installed ubuntu and ispconfig3 following one of those "perfect server" guides. Everything appeared to go smoothly. However, when connecting to my email accounts on the server through thunderbird, I can receive email but cannot send email. I can send and receive email via the webmail webpage. Postfix is operating on port 587 as I'm on comcast and that's what they require for outgoing mail. The error that I get in /var/log/mail.log: and the error that I get in thunderbird: I imagine that it's a misconfiguration of dovecot or postfix but as I'm new to linux and system administration, I have no clue regarding how to fix the issue or how to go about troubleshooting the issue. Any advice on the issue is greatly appreciated.