I've moved from constant contact to Drupal Simplenews/Mimemail/SMTP. Previously the open rate was around 50% for constant contact, but now it's 4-5% for the same list via the mentioned setup. Mail is getting out from the server, but it's having an issue anyway.

Here's the setup: -The e-mail list consists of approximately 80,000 addresses which is queued at 10,000 e-mails per cron run (which runs hourly).

-The server is a Dual Core2Quad machine with 2GB of RAM.

-When mail is being sent, the mail queue will usually go up to ~1000 at the beginning of the hour before reducing to ~250 by the time the next cron occurs.

-Newsletter is themed to display custom style for newsletter on send

-Newsletter is received by some, but appears to be bounced by many (based on low open rate_

-I've added SPF, domain keys, and a PTR record to the DNS

-Server hostname (listed in ptr) is different from hosted domain

-Very low spam number via Spamassassin

-IP and domain are not blacklisted

-Mail goes out via SMTP module on delivery.

Any ideas?