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Wanting to make sure I've done everything I can to prevent our legitimate email from being incorrectly marked as spam by other companies:

Exchange 2010 with SP1, no major changes in 6 months.

I've run email for this particular 30-user business for nearly a decade, but the last few months their emails are starting to be caught by their customers/partners spam tools. These are human to human emails outgoing from my Exchange servers to other companies. When one or two starting saying company X or Y isn't receiving my emails I think it's a fluke, but now it seems to be up to 5 people internally having issues with 1/2 a dozen of their customers/partners on every email, sometimes just new emails, sometimes replies.

  • I have a proper PTR record matching hostname
  • My email domain matches MX domain name and the EHLO response
  • On no blacklists according to mxtoolbox.com
  • senderscore.org is all good and shows score of 100
  • SPF/Sender ID setup correctly
  • Exchange 2010 doesn't support DomainKeys so I'm not doing that
  • No spam or marketing emails are sent from this server/IP
  • All sending email is human generated
  • IP is from a colo not residential ISP
  • no complaints of email not getting to email providers (hotmail, gmail, yahoo, etc.)

Any further ideas? At this point all I have to say to people is "totally out of our control", unless I want to work with each company to find out their anti spam vendor and contact each one for resolution...

Thanks for any ideas!

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Are any of them using a good spam filter that says why it was caught? I've been battling the same of late; spam filters ratcheted up higher than ever and catching our real e-mail. – Chris S♦ Jul 22 '11 at 0:20
Chris S: I'm working on that part now. – Bret Fisher Jul 23 '11 at 4:09
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2 Answers

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I've seen issues crop up when the company asks all employees to use a specific 'signature' block on their message that includes a gif or jpg (like the company's logo). That little embedded image can pump the spam score up needlessly.

It wouldn't hurt to ask one of the affected employees to resend a message that was caught in a spam filter to a Yahoo or Gmail account and then inspect the header after it arrives there. It could reveal those little issues that are below Y/Gmail's thresholds, but that may be over the threshold with smaller outfits that are being overly aggressive in filtering.

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we do have some users doing that. I'll ask them to change and give it a shot. – Bret Fisher Jul 23 '11 at 4:09
This may have been the issue. They had a standard signature they used that included multiple small images that were clickable href's. Once they took out the multiple clickable images email went through. I've only got a few people telling me they've tested it so far. Great tip guys. – Bret Fisher Aug 1 '11 at 4:24
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up vote 0 down vote

You need to find out the who/what/when/where. You could enable smtp logging if you are sending directly from the server. It could be something as simple as a signature. I once had a user that used the word "specialist" in his sig. ---> speCIALISt ---> CIALIS see what happened there.

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