About SMTP Banner Test
This test opens a TCP connection to the highest-priority MX on port 25. Many cloud networks block outbound port 25, so a failed connect can be a firewall policy rather than a dead mail server.
Connect to the primary MX host on port 25 and read the SMTP banner / EHLO response when the network allows it.
This test opens a TCP connection to the highest-priority MX on port 25. Many cloud networks block outbound port 25, so a failed connect can be a firewall policy rather than a dead mail server.
Outbound port 25 is commonly blocked to prevent spam. Try from a mail-allowed network, or rely on MX/DNS checks instead.