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Journal Journal: Hotmail filters sent emails to spam 6

hotmail (Microsofts webmail service) is filtering mail written in (a mac OS X) program directly to the junk mail folder and I figured out what they are doing.

It started when some mail that went out of a mail server I manage was incorrectly filtered by hotmail as junk email. In the interest of knowing what was going I performed several tests to obtain the details of the problem.

First, I tried sending from several other methods. This included sending from other mail programs in unix, webmail, etc. Some of these under the same routing path through my firewall. All of the other mail programs, whether by webmail or smtp, sent and were not filtered to junk. But, was consistantly filtered to junk.

So, I decided to try and fool hotmails filters so they would think it was coming from and see if I could find what they were filtering based on.

In the headers of the email there are two specific lines that tell you the email was generated by and apple product and specifically:

X-Mailer: Apple Mail (2.733)
MIME-Version: 1.0 (Apple Message framework v733)

At first I tried scripting, in PHP, scripts to send to a test email address and see what was identified as spam. Using mail(), which uses qmail on my setup, and sendmail itself in another setup caused the mail to not be filtered. Hotmail seems to realize mail is from these programs and not so it is not filtered.

Next, I tried scripting so that the email interacts directly with a known good smtp server. In my case I used comcasts mail server as they are my internet provider. I used a script already generated to do smtp that can be found here. When I added:

X-Mailer: Apple Mail (2.733)

to the header it is filtered to the junk folder in hotmail.

So, hotmail looks for this header and to make sure the email is not from sendmail or qmail. In these cases the email is filtered to the spam folder.

REAL NICE Microsoft.

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