It seems now, more than ever, the major service providers have cracked down on SPAM and really focused on filtering.
This is a huge concern for website's that require email validation, as users who do not receive instant emails are generally put-off the service all together.
So, my question is;
What are the most important keywords and headers required in an email to ensure the delivery to the major email service providers.
Also any other techniques; links to whitelist forms that allow you to submit your servers' IP(s)..etc will be a bonus.
1) Don't use a fake address, that's reeks of spam
2) Set up DomainKeys for your domain
3) Set up SPF for your domain