So I had moved to a new server, but noticed that I couldn’t send emails anymore.
I use SMTP, but I always got this error message.
SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
Finally found out that in my DirectAdmin “ConfigServer Security & Firewall” one difference with the old server.
SMTP_Block was ON
Once I put this on OFF, I could send invoices on the new server.
But I see you can put here something
SMTP_ALLOWUSER = SMTP_ALLOWGROUP = mail,mailman
Do I need to put here something to let it work, so SMTP_Block can be back ON