Mail Server can receive but cannot send to external mails

Support and Discussion
1

setup:

  • aws ec2 instance hosted mail server
  • smtp is configured to use port 587

scenarios:

  • receiving mail from internal (same domain mail) and external (other mail like yahoo or google mails) is ok
  • sending mail to internal (same domain mail) is ok
  • sending mail from to external (other mail like yahoo or google mails) is NOT ok

Right now I cannot figure out the issue but i confirmed that the port for smtp is configured to be open correctly.

2

You have to request them open mailing ports. To prevent spammers they block them by default no matter your own firewall those are open.

3

hi I have confirmed that port 587 is open though I also tested it is not restricted unlike port 25