Probably after an upgrade, Cloudron does not send emails anymore, thereby preventing the creation of new users.
In the Email / Status menu of Cloudron, the initially green flags for DKIM record and SPF record turned to red errors. The SMTP status provides error messages like "Connect to smtp.o2.ie timed out. Check if port 25 (outbound) is blocked". All outbound ports are open.
After clicking the "Send Test Email" button, in the email server logs I see errors including "DNS lookup failure: Error: queryMx ETIMEOUT mydomain.com" where mydomain.com should be replaced with my domain.
If I ssh to the server, running the command "systemctl status unbound" says that the service is active (running). The command "host -t txt mydomain.com" provides the correct return.
However, if I go the the terminal of a specific app, the command "host -t txt mydomain.com" returns "connection timed out; no servers could be reached".
I have Cloudron 3.5.4 on ec2.
In the Email / Outbound Relay menu, the setting is Built-in SMTP server. I tried changing to Amazon SES or External SMTP server, but the changes are not applied, probably because the connection with these external servers is not possible, possible of the same DNS issue.
How can I solve this issue? Not being able to create new users is blocking me to use Cloudron.