Avoiding spam filters for legitimate mail

Question

Duplicate of http://stackoverflow.com/questions/371/how-do-you-make-sure-email-you-send-programmatically-is-not-automatically-marke

Initially I planned to send emails from my website as html (i.e. content-type: text/html;) but I just thought about something today, won't it better to send emails as plain text, i.e. content-type: text/plain;, so that the chances of my mail messages ending up in the spam/junk folder become less, I was thinking that this must be one the rules used by spam filters on popular webmail services like gmail, yahoo and hotmail, what do you think?

Answer 1

In my experience, most anti-spam systems will score HTML's Hamminess slightly below plaintext, but there are much more important things to consider that affect deliverability:

• make sure you have a valid Reverse DNS configuration for your mail server, or you will be undeliverable to many domains.
• investigate adding an SPF record to your DNS zone file. This helps, particularly with GMail.
• Look into DomainKeys, if it's available on your platform. This is essentially a cryptographic signature attached to your outbound mail, so it proves that you are the person who sent it.
• Review your message content and make sure you aren't using any words (particularly in the subject line) that are obvious spam indicators.

Answer 2

I think to be safe, other than what Tim Howland recommended, you could always first send a plain text email welcoming the person and asking to put your domain in their email safe file. I see this happen a lot with big companies; I get a plain text email saying "Welcome, make sure [email protected] is in your safe-email file."

I can't say that your plain text email wouldn't be considered spam in the first place, but at least this is an easy first step to ensure your HTML emails get through.