false return always

[devbugice]

false return with hotmail and gmail

[scream314]

Hey, please check if you have outbound TCP port 25 open, many providers block it.

[kevflynn]

Hey @scream314 - thanks for the answer. How do I check that? If it's not open, how do I open it?

[scream314]

@kevflynn
First you should find a working mailserver on the internet to test (or if you have one, you coluld of course us that):

# dig mx google.com

; <<>> DiG 9.10.6 <<>> mx google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22222
;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;google.com.			IN	MX

;; ANSWER SECTION:
google.com.		599	IN	MX	30 alt2.aspmx.l.google.com.
google.com.		599	IN	MX	10 aspmx.l.google.com.
google.com.		599	IN	MX	20 alt1.aspmx.l.google.com.
google.com.		599	IN	MX	40 alt3.aspmx.l.google.com.
google.com.		599	IN	MX	50 alt4.aspmx.l.google.com.

;; Query time: 78 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Tue Jan 21 09:34:21 GMT 2032
;; MSG SIZE  rcvd: 136

Then use netcat (or telnet or something equivalent) to determine if you can reach its port 25:

# nc -zv aspmx.l.google.com 25
found 0 associations
found 1 connections:
     1:	flags=82<CONNECTED,PREFERRED>
	outif en0
	src 127.0.0.1 port 59360
	dst 66.102.1.27 port 25
	rank info not available
	TCP aux info available

Connection to aspmx.l.google.com port 25 [tcp/smtp] succeeded!

If the port is unreachable and it is not blocked by your firewall, then most probably your ISP is blocking it. If this is the case you could either contact them, and ask them to unblock (for example with my ISP I can disable the block by logging in in my ISP account and unticking a checkbox); or you could rent an external server and forward your mail traffic through it (doing so you would have many options, you could either simply redirect outbound port 25 traffic with sshuttle or use mailservers configured as relay hosts and relay your mail traffic through your external server, etc...).
But the easiest method is if your ISP simply removes the restriction.

[ThibaultJanBeyer]

Gmail seems to block these ports… So the tool is not really useful?

[knoxcard]

Gmail works for me. Although, outlook.com/hotmail.com always appears to be returning false.

[knoxcard]

You know what would be cool?

If this module would let you know if port 25 is blocked.
It should output DNS diagnosis.