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How could I prevent my mail from being recognized as spam?

I have a web server that sends legitimate transactional email in high quantities. A reasonable percentage of users report that they never receive the emails. For every message sent, there's also a blind carbon copy going to an unfiltered email box on a different provider that I review to ensure the server actually sent the emails. All of the emails make it to my bcc box, so the server is sending the emails properly. It seems to be a spam filtering problem at other email providers.

The hosting provider for the web server indicates a reverse dns lookup has been set at their level linking the emails ip address properly to my server and domain.

Question: Is there anything else I can do to improve the rate that 3rd party service providers are filtering the emails I'm sending? Is there anything I can set on the DNS that I control to show that the server sending the emails is legitimate?


1 Answer 1


Usually, I would recommend using a third party service to handle your transactional emails. For the most part, the time you spend worrying about email infrastructure and deliverability are better spent building out your product and working with your customers. Some of the best options are SendGrid, Postmark, and Mailgun. Using one of these services can give you some valuable metrics on deliverability as well, so you can know for sure where your emails end up. That said, here are a few ways you can improve your deliverability rates on your own:

1. Use a spam checkers on all your emails

You should run your emails through one of these services before sending them out. This will check for certain trigger keywords, verify your SPF records and domain keys record are correct, etc. IsNotSpam.com and ProgrammersHeaven.com are two options.

2. Make sure your IPs are not blacklisted

Sometimes the IP address you're using to send email gets flagged as a spam address and blacklisted. You can use a number of tools to check and see if you're on the list. Some of the best ones are blacklistmonitoring.com and http://www.dnsstuff.com/.

3. Make Sure Your DKIM, SPF, Sender-ID and Domain Keys are Setup Properly

You will want to make sure your email server supports these protocols and that they are properly implemented.

4. Make sure your compliant with CAN-SPAM

If your violating the CAN-SPAM guidelines, you're a lot more likely to have your email flagged as spam and therefore end up in the black-hole spam filters. More details on that here

In the interest of full disclosure, I work for SendGrid as a devloper evangelist.

  • Thanks, the idea of running the emails through a spam checker should have been obvious. It helped quite a bit in identifying negative modifiers. I think the biggest improvement came from cleaning up the headers. So far reports of non-delivery have improved a lot since the changes.
    – JMC
    Commented Apr 13, 2012 at 16:41
  • No worries, happy to help.
    – Swift
    Commented Apr 13, 2012 at 20:18
  • About SenderID: Microsoft says that "Hotmail has stopped checking SenderID and starting checking SPF as that is what is what is required by DMARC. This leaves only on-premise Exchange servers." So maybe not worth the effort. See blogs.msdn.microsoft.com/tzink/2013/04/24/…
    – lajarre
    Commented Sep 18, 2016 at 22:33

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