Testing an Outbound Port from Your Web Host

Mark Berry December 6, 2014

Recently I decided to install the WP Mail SMTP plugin into a WordPress blog to get around the shared server being blacklisted. The idea is to get WordPress to send emails through an external mail server after authenticating. However on one server, the test mail was failing:  I was getting a timeout error.

After a little googling, I learned that some web hosts block certain outbound ports. But how to confirm whether my host was blocking port 587, used for SMTP over TLS?

Testing with portquiz.net

Enter portquiz.net. This brilliantly simple service is listening on all TCP ports and will respond to requests from http, telnet, nc, curl, and wget. Visit portquiz.net for examples.

I opened a Putty SSH session at each host and tested outbound port 587.

At one host, it fails:

netquiz 1

That explains why I couldn’t send email from that host using WP Mail SMTP.

Fortunately, at the host that is blacklisted, port 587 is open and WP Mail SMTP works:

netquiz 2


  1. Javier   |  February 02, 2015 at 10:09 pm

    Dear friends i have wordpress with godaddy and i cant configured, do you know how port its a correct but godaddy hosting?
    thank you
    im from mexico

  2. Mark Berry   |  February 02, 2015 at 10:17 pm

    Javier, I suggest you contact Go Daddy support.

  3. sujit   |  February 06, 2015 at 7:57 am

    I have my port 587 test successful, even then unable to do the successful authentication.

  4. Mark Berry   |  February 06, 2015 at 9:03 am

    sujit, email authentication is a big topic and there could be many reasons for a failure: unauthorized From address, bad password, etc. This post is only about resolving a timeout error that was caused by a blocked port.

  5. Jason Hendriks   |  February 11, 2015 at 4:15 pm

    That’s a great tip! Though the link that I followed to get here (https://wordpress.org/support/topic/gmail-smtp-error-could-not-authenticate?replies=6) clearly said “SMTP Error: Could not authenticate” … and that’s not a connection issue.

    I wrote a WordPress SMTP plugin with an integrated port tester, Postman SMTP.

  6. Mark Berry   |  February 12, 2015 at 7:59 am

    Jason, that looks like a nice plugin! https://wordpress.org/plugins/postman-smtp/

  7. Jasa   |  November 26, 2015 at 9:24 am

    I have tried port 465, 25 and 587 blocked . My server Can not send email. What should i do tp lift up this error

  8. Mark Berry   |  November 26, 2015 at 9:36 am

    Jasa, I suggest using an SMTP plugin to send through your email server. I blogged about how I modified one of them: http://www.mcbsys.com/blog/2015/01/increasing-the-wp-mail-smtp-timeout/.

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