PHP mail messages seen as junk because of image on certain domain

[optik]

I've been trying lots of tests to try and figure out why some e-mails generated by PHP mail() are going to junk in outlook.

I finally found out it was only when images from my domain were included, if the e-mail had a link to an image on another domain it works fine.

I'm pretty sure the domain is blacklisted so don't understand why only images on my domain are being a problem.

[enigma1]

Perhaps the IP of your site where the images are located is different than the one that sending the emails.

[optik]

But when linking to an image on a totally different server the e-mail wasn't blocked.

The test I did to prove this was get an image from and e-mail that wasn't being blocked put that in my e-mail, which worked, then upload that image to my own server and then just changed the domain in the image reference from the original site to my server, that change stopped the e-mail getting through.

So <img src="http://www.site.com/image.gif" width="90" height="90" alt="">
worked and <img src="http://www.mysite.com/image.gif" width="90" height="90" alt=""> didn't.

[enigma1]

So if the IP of the mysite.com is blacklisted and there is a filter that checks the links in the email, it can be the reason that the email is blocked.

You get the IP of the domain that is in the link of the image, then you check if it's blacklisted. If it is, you throw it in the junk email folder.

[optik]

It does act like the IP is blacklisted but every checker I use shows it is ok and there is no reason why it should be black listed.

[enigma1]

There are so many databases and methods, some aren't too reliable. It maybe not be the outlook but the receiving end could inject additional headers.

Try on a different server to retrieve the emails or use webmail and then check the mail headers and see if they're identical.