Today one of my clients inbound has stopped receiving email. They are getting either no emails or senders receive a bounce back.
Below i one of those bouncbacks.
From: System Administrator - Boston <postmaster@%%%%.com>
Date: February 21, 2011 11:15:10 AM EST
To: Joseph Jennings <Joseph.Jennings@%%%%.com>
Subject: Delivery Final Failure Notice
Can not deliver the message you sent. Will not retry.
The following addresses had delivery problems
<email@example.com> : Reply from XXX.psmtp.com[188.8.131.52]:
<<< 500 5.3.3 Unrecognized command
Exchange Remote Connectivity Analyser says this...
Testing inbound SMTP mail flow for domain firstname.lastname@example.org.
ExRCA failed to test inbound SMTP mail flow.
Attempting to retrieve DNS MX records for domain domain.com.
One or more MX records were successfully retrieved from DNS.
Testing Mail Exchanger remote.domain.com.
One or more SMTP tests failed for this Mail Exchanger.
Attempting to resolve the host name remote.domain.com in DNS.
The host name resolved successfully.
Testing TCP port 25 on host remote.domain.com to ensure it's listening and open.
The port was opened successfully.
Attempting to send a test e-mail message to email@example.com using MX remote.dcwcorp.com.
Delivery of the test message failed.
The server returned status code 500 - Syntax error, command unrecognized. The server response was: 5.3.3 Unrecognized command
Message: Syntax error, command unrecognized. The server response was: 5.3.3 Unrecognized command
at System.Net.Mail.DataStopCommand.CheckResponse(SmtpStatusCode statusCode, String serverResponse)
at System.Net.Mail.SmtpConnection.OnClose(Object sender, EventArgs args)
at System.Net.Mail.SmtpClient.Send(MailMessage message)
They are using Postini Spam filtering. I have since disabled this AND changed MX's back to point directly at their server, same thing.
This system has been working perfectly for months. This is the first time there has been an issue like this.