Port 2525 is used for secure submission of emails for delivery by modern ESPs. Unlike other SMTP ports, you will not find the port block issue with port 2525. As this is a non-standard port for SMTP, so it is not getting monitored extensively and are allowed on consumer IPs and Cloud hosting providers like Google Compute Engine. It is not an official SMTP port and it is not sanctioned by the IETF nor IANA. It is an alternate port which has the same functions as port 587.
Pepipost supports TLS on port 2525, this you can verify by connecting to smtp.pepipost.com and issuing an “ehlo” command. 250 STARTTLS in output confirms that the endpoint accepts TLS connection requests.
How to check if Port 2525 is blocked on your network?
There are some common error messages which you might encounter;
- 2014-08-31 17:13:00 SMTP ERROR: Failed to connect to server: Permission denied (13)
- Connection unexpectedly closed: timed out
- Timeout::Error (execution expired)
- S: SMTP ERROR: QUIT command failed: Connection: closed
- SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
- Mailer Error: SMTP connect() failed.
There can be more… this is just a sample list. All these are errors from different programming environment, but all lead to a common problem that your outgoing port 465 might be blocked.
There are multiple ways to check if a particular port is blocked on your network, the simpliest one to check this is using the telnet command on your terminal as shown in the above screenshot. If Port 2525 is blocked, you will get a connection error or no response at all.
Trying 64.13.192.208...
telnet: connect to address 64.13.192.208: Connection refused
telnet: Unable to connect to remote host
There is one more tool outPorts on Github, which is very user-friendly when it comes to checking the outbound ports. But, yes it has multiple dependencies that need to be installed to start using.
Once, installed just run the below command to check if the port is opened or closed:
outPorts 25
When to use it?
Most ESPs support the use of Port 2525 as an alternative to port 587 for SMTP. Port 2525 also support TLS encryption.
Difference between port 2525 and 25/467/587
Recommended: Keep regular track of your IP/domain reputation and ensure they don’t fall into a blacklist database. We developed a tool that will help you check your blacklist status with over 100+ databases.
