Errors in HTML tags could send your e-mail into the bulk folder

Mail marketers often believe that any e-mail that has in its subject or body the words “free” would be filtered. But this is not always true. Even though certain mails, which include different combinations of words containing “free” are filtered, the ISPs could often block your e-mails for other well-known reasons.

As a good example one can use the HTML code. If you use in the e-mails you send incorrect or outdated code, domains such as Hotmail and AOL would surely block it, either send to bulk or junk folders. Even if you see that your email has rendered correctly, and looks just fine to you, Pivotal Veracity, a delivery-monitoring service provider, estimates that nearly every message sent in HTML doesn’t fully comply with the World Wide Web Consortium standards.

Every ISP manipulates differently the e-mails it receives, and therefore the messages that are passed at one destination can be easily blocked at another ISP. Because very many spam mails are sent in HTML format, with heavy use of HTML syntax and formatting errors, in order to trick some of the ISPs, many spam filters will simply delete or send to bulk all the messages that do not correspond to the W3C standards. Well, some infractions are minor and will allow the passage of the mail. An example of such an infraction could be the omission of the tag “alt”, which describes the content in an image tag. Many other faults can send your e-mail the bulk folder.

Pivotal Veracity recently tested a great number of HTML email messages in order to see if they were accepted or rejected by the most popular ISPs. Here are the results if the tests:

• If you use a tracking beacon below the closing HTML tag, your e-mail will be filtered and sent to bulk folder on MSN/Hotmail
• A badly constructed boundary between the text and HTML portions of a multipart e-mail message will send your e-mail at the bulk folder in MSN/Hotmail
• Using hex-encoded characters in URLs (for example by substituting the “%20” code for a space with its hex equivalent) may get the e-mail blocked or into the bulk folder at AOL, CompuServe and MSN/Hotmail.
• Usage of a decoy link that shows one URL in the e-mail but actually redirects you to another URL when clicked will also get the e-mails rejected or sent into the bulk folder at MSN/Hotmail