How do you make sure email you send programmatically is not automatically marked as spam?
Use email authentication methods, such as SPF, and DKIM to prove that your emails and your domain name belong together, and to prevent spoofing of your domain name. The SPF website includes a wizard to generate the DNS information for your site.
Check your reverse DNS to make sure the IP address of your mail server points to the domain name that you use for sending mail.
Make sure that the IP-address that you're using is not on a blacklist
Make sure that the reply-to address is a valid, existing address.
Use the full, real name of the addressee in the To field, not just the email-address (e.g. "John Smith" <[email protected]> ).
Monitor your abuse accounts, such as [email protected] and [email protected]. That means - make sure that these accounts exist, read what's sent to them, and act on complaints.
Finally, make it really easy to unsubscribe. Otherwise, your users will unsubscribe by pressing the spam button, and that will affect your reputation.
That said, getting Hotmail to accept your emails remains a black art.
Sign up for an account on as many major email providers as possible (gmail/yahoo/hotmail/aol/etc). If you make changes to your emails, either major rewording, changes to the code that sends the emails, changes to your email servers, etc, make sure to send test messages to all your accounts and verify that they are not being marked as spam.
You can tell your users to add your From address to their contacts when they complete their order, which, if they do so, will help a lot.
Otherwise, I would try to get a log from some of your users. Sometimes they have details about why it was flagged as spam in the headers of the message, which you could use to tweak the text.
Other things you can try:
- Put your site name or address in the subject
- Keep all links in the message pointing to your domain (and not email.com)
- Put an address or other contact information in the email