MailerQ - MailerQ is a high performance Mail Transfer Agent (MTA) designed for delivering large volume email messages at very high speeds.
Spamihilator - The free Anti-Spam-Filter Spamihilator removes more than 98% of spam mails before they even get into your inbox.
turboSMTP - turboSMTP is a reliable, powerful, easy-to-use SMTP server that maximizes the deliverability of all...
Mailwasher - Over 8 million people use MailWasher as their spam filter
SMTP - SMTP provides scalable affordable email infrastructure for all your sending needs.
SPAMfighter - SPAMfighter and Microsoft have built the strongest and most effective anti spam filter for Outlook, Windows Live Mail, Outlook Express & Thunderbird