Status Check states port 25 is blocked, but nmap says otherwise

[alento]

@openletter

In the context of this thread, inbound is a server outside of MiaB trying to connect to MiaB on port 25.

Correct.

@openletter

Outbound is MiaB trying to connect to another server on that server’s port 25.

Also correct, but …

@openletter

Not being able to send mail may indicate that MiaB cannot connect to another server on that server’s port 25.

Or … the real reason that this is an issue MOST ALWAYS is because the provider has blocked outbound connections to port 25. Not because the inbound server is blocking them … the outbound server will not allow connections to be made OUTBOUND on port 25.

Hence, my suggestion for the OP to ticket his provider again to confirm that they actually DID unblock port 25 capabilities.

[openletter]

When requests to destination port 25 are blocked, this is the output:

$ telnet box.occams.info 25
Trying 94.76.202.152...

I can easily verify this as my home ISP blocks such requests, as does another hosting ISP that I have recently started using but am not currently concerned with correcting the issue.

However, from any of my Vultr instances I get the following output from telnet:

$ telnet box.occams.info 25
Trying 94.76.202.152...
Connected to box.occams.info.
Escape character is '^]'.
220 box.occams.info ESMTP Hi, I'm a Mail-in-a-Box (Ubuntu/Postfix; see https://mailinabox.email/)

So telnet can be used to test if this is being blocked, and the posts above indicate this is not the case for their MiaB hosting provider.

[davness]

The status checks failure for port 25 means that the box is unable to connect to aspmx.l.google.com. If you somehow are able to connect to other servers, this may indicate Gmail is specifically blocking connections from you or your ISP (but it could be something else, too).

Whats your hosting provider?

[openletter]

Okay, so I didn’t know exactly how those status checks work. There may be something that Google, specifically, is blocking.

You could try:

$ telnet aspmx.l.google.com 25
Trying 2607:f8b0:4023:1004::1a...
Connected to aspmx.l.google.com.
Escape character is '^]'.
220 mx.google.com ESMTP r8si8673280oth.273 - gsmtp
quit
221 2.0.0 closing connection r8si8673280oth.273 - gsmtp
Connection closed by foreign host.

And see if the output matches above or if it never connects.

[LightChain09]

Okay, so I wrote a ticket to my provider telling him about the issue. They tried giving me a new IP Address and checked again on the blocking of port 25. Somehow everything is fine now and I really don’t know why. I’m not complaining just confused. Maybe they didn’t really unblock it.