I received a report from a couple of users that email they were sending wasn't being delivered to recipients, though they weren't receiving any bounced messages or any indication that their email was not being delivered. Their email clients were sending email to smtp.atlanticbb.net. When I sent email from the same IP address to that Atlantic Broadband Simple Mail Transfer Protocol (SMTP) server addressed to several email accounts I maintain for email troubleshooting on a number of free email services, such as Gmail, none of them reached their destinations, even though as far as the email client was concered, they were successfully delivered to the Atlantic Broadband SMTP server.
Examining the message headers from an email sent from a tech support person at Atlantic Broadband, whom I contacted on June 1 regarding the problem, to my Gmail account (see Viewing message headers in Gmail), I learned that Atlantic Broadband uses Echo Labs to handle their email. I saw the following in the message headers:
Received: from cluster1.echolabs.net (mail.atlanticbb.net. [188.8.131.52]) by mx.google.com with ESMTP id l144si10145927ybf.89.2016.06.01.19.40.53
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