Cannot telnet to port 25 on EC2 instance

Question

My security group has the following:

>22 (SSH)   0.0.0.0/0   
>80 (HTTP)  0.0.0.0/0   
>143 (IMAP) 0.0.0.0/0   
>443 (HTTPS)    0.0.0.0/0   
>995 (POP3S)    0.0.0.0/0   
>465 (SMTPS)    0.0.0.0/0   
>25 (SMTP)  0.0.0.0/0

Running a netstat on the server shows the following:

>Active Internet connections (servers and established)
>Proto Recv-Q Send-Q Local Address           Foreign Address         State      
>tcp        0      0 127.0.0.1:9000          0.0.0.0:*               LISTEN     
>tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
>tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN     
>tcp        0      0 0.0.0.0:25              0.0.0.0:*               LISTEN     
>tcp        0      0 10.211.30.202:44025     194.14.0.125:6667       ESTABLISHED
>tcp6       0      0 :::995                  :::*                    LISTEN     
>tcp6       0      0 :::110                  :::*                    LISTEN     
>tcp6       0      0 :::143                  :::*                    LISTEN     
>tcp6       0      0 :::22                   :::*                    LISTEN     
>tcp6       0      0 :::25                   :::*                    LISTEN     
>tcp6       0      0 :::993                  :::*                    LISTEN     

And when I try and access the box from the outside world, I get nothing.

>thedude:~ root$ telnet mail.sd0a.com 25<br />
>Trying 107.20.235.215...<br />
>telnet: connect to address 107.20.235.215: Operation timed out<br />
>telnet: Unable to connect to remote host<br />

Anyone have any positive experiences with Amazon EC2 instances and getting mail to a state where it will work? Its worth noting that via command line, mail seems to go through. System is Ubuntu 12.04.1 LTS if that matters.

Answer 1

Might be your ISP filtering outbound connections to port 25/tcp in order to prevent botnet spam.

Answer 2

To eliminate the obvious: Have you tried

• connect to another port other than 25?
• connect to another new ec2 instance, port 25? (straightforward task to duplicate it on EC2)
• connect from another machine (or your friend's PC) to sd0a.com:25?
• traceroute to identify where the packets are dropped?
• setup postfix on port 2525 (remember to add that into Security Groups)
• ufw* on Ubuntu. (Default is off... but good to check)

As far as I can tell, all IP addresses on Amazon EC2 are blacklisted in spamhaus.com (and a lot of other anti-spam list). Hence most likely your ISP is blocking these packets, if so it is IP block or port block?