Cannot send through custom SMTP server, firewall blocks the add-on's IP
Our add-on cannot access the SMTP port in case you are using your own SMTP server protected by a firewall. In order to work around this, you need to allow certain IP addresses on your firewall.
Current IP addresses
Email This Issue is currently running on Amazon EC2 instances. If you are using a firewall to filter incoming connections to your IMAP or SMTP servers, then please add these IP addresses to your firewall configurations based on your cloud instance's residency:
US residency IP addresses:
52.27.95.185/32
54.188.78.95/32
52.12.208.63/32
EU residency IP addresses:
18.158.85.162
3.121.79.174
3.72.199.195