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.


SMTP Smarthost to Office 365 and Gmail

Mark Berry October 9, 2014

I use the Windows SMTP service to relay some mail to Office 365 and, from another site, to Google Apps Gmail. Here are some notes and links on both.


Windows SMTP Service Not Sending Messages

Mark Berry October 9, 2014

On a Server 2012 R2 Essentials machine, I set up the SMTP service with a smart host to relay messages. The setup was identical to a working setup at another location. I could see in the SMTP logs that the server was accepting the messages, and they were accumulating in the Queue folder, but the logs did not show any attempt to make outbound connections.


Office 365 SMTP Relay: What KB2600912 Doesn’t Tell You

Mark Berry June 13, 2013

Yesterday I was trying to set up Office 365 to relay email messages from Line-of-Business applications. I was following the smart-host method described in Microsoft KB2600912:  How to set up an SMTP relay in Office 365. However that article was missing some key pieces of information.


Exchange 2007 SMTP TLS Error Oddly Resolves Itself

Mark Berry June 11, 2012

I noticed that my SBS 2008 Server was generating 70 or 80 of these errors every day since May 30:


Testing SMTP Using Telnet

Mark Berry August 17, 2007

I’m trying out a hosted anti-spam solution. This service works by becoming my public-facing mail server (DNS MX record), and relaying non-spam mail to the mail server in my office.

Due to a configuration error, I lost about 15 hours of email–the host wasn’t relaying for my domain. Email was bouncing with the message “553 Relaying is not supported”.

Lesson learned (with thanks to Ezra Herman):  before switching DNS, use Telnet to test the connection to the host and make sure it is accepting email for my domain. Here’s how to do it:

XFOR: Telnet to Port 25 to Test SMTP Communication

The configuration is fixed, I sent myself an email using a Telnet session to the anti-spam host, so now I can update my DNS!

Update 4/28/2009:  This TechNet article explains testing SMTP with Telnet when authentication (but not SSL encryption) is needed:

How to Use Telnet to Test SMTP Communication

Update 12/18/2009:  I tried to use Telnet to test sending a message to Go Daddy’s email server (smtp.secureserver.net). But whenever I typed

MAIL FROM:Admin@test.com

as described in KB 153119, I got this message:

501 #5.5.2 syntax error 'MAIL FROM:Admin@test.com'

I noticed in a MailEnable SMTP log that it encloses email addresses in angle brackets. Sure enough, when I typed

MAIL FROM:<Admin@test.com>

I got the expected response:

250 sender <Admin@test.com> ok



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