Some email clients can fake the sent email’s X-mailer text. This is a very dangerous option to choose if you want your emails to stay away from spam folder.

When the email is composed, the X-mailer text is not the only common field filled by the origial sending software: there is also the X-MimeOLE field.

Microsoft Outlook Express attaches this MimeOLE: V6.00.2900.3138. This number depends obviously by the version of Outlook Express we are using, but not many bulk emailers can fake the MimeOle field too. Composing an email message pretending to be read as a common Outlook Express’ email and mistaking the final composition can result in a catastrophic spam score (if we were playing monopoly this means go straight to jail!).

If we are sending our email with a powerful bulk emailer that enables to change the X-Mailer text, and we pretend to be sending from Outlook Express in order to optimize our inbox rate, we are doing a great mistake: being caught by the Forged_Mua_Outlook SpamAssassin common spam rule after our email sending operation causes our email to get 3.4 spam points (very high spam rate, and very bad)…

Plus, if we are not careful in email composition, we can get additional 2.4 points for the Forged_Outlook_tags broken SpamAssassin common Rule, since Outlook has a very particular way of building html for the emails, it’s pretty easy to see if an email has been composed by another email client’s html composer.

Conclusions:
Faking X-mailer field is not a useful way to raise email inbox rate, even though it seems appealing. Keeping your email client or bulk e-mail sender identity clean (or at least leaving empty the x-mailer field) is the best option for your clear conscience and for your inbox rate.

Tests: you can do your own tests with our SpamAssassin engine spam checker software: try to modificate the x-mailer (you can try with SendBlaster Free Bulk Emailer) text and spam check your mail, then leave the original x-mailer text, and spam check your mail again. Then take a clean Outlook Express email and spam check it, you will notice heavy spam points decreasing.