All "Email Status" fields are green and I'm able to send emails from firstname.lastname@example.org to any email address plus receive emails from any email address that belongs to my domain, e.g. email@example.com.
However, emails from external addresses like firstname.lastname@example.org do not end up in my email@example.com mailbox. I wasn't able to find anything in the logs/even logs etc. And strangely emails from external addresses to firstname.lastname@example.org (or really any email @mydomain.com) do not bounce either. There is no error message that the delivery failed whatsoever.
Unfortunately I don't even know where I should start looking for the source of the problem. So really any ideas would be appreciated!
I'm using Roundcube for the emails, Mailgun for outbound emails, and Namecheap for my domains.
Update: I just discovered that I got a delayed error message a few days ago that says: "The recipient server did not accept our requests to connect."
Just found the solution here: https://forum.cloudron.io/topic/1279/receive-email/4
The problem was that AWS EC2 instances close port 25 by default. As soon as I opened it in the AWS console, I was able to receive emails.