Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail. It attempts to be fast, easy to administer, and secure. The software is also known by its former names VMailer and IBM Secure Mailer.

NikaMail is described as 'Portable, extendable, zero-config email server. It is designed to perform automation tasks, provide access to mailboxes (port 110), serve as a mail transfer agent (port 587) and mail exchange service (port 25). NikaMail supports TLS' and is a Mail Server in the online services category. There are more than 10 alternatives to NikaMail for a variety of platforms, including Linux, Mac, Self-Hosted, Windows and BSD apps. The best NikaMail alternative is Postfix, which is both free and Open Source. Other great apps like NikaMail are Haraka, Exim, OpenSMTPD and Sendmail.
Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail. It attempts to be fast, easy to administer, and secure. The software is also known by its former names VMailer and IBM Secure Mailer.

Exim is a message transfer agent (MTA) developed at the University of Cambridge for use on Unix systems connected to the Internet.
OpenSMTPD is a FREE implementation of the server-side SMTP protocol as defined by RFC 5321, with some additional standard extensions. It allows ordinary machines to exchange e-mails with other systems speaking the SMTP protocol.
Sendmail is a general purpose internetwork email routing facility that supports many kinds of transfer and delivery methods, including the Simple Mail Transfer Protocol (SMTP) used for email transport over the Internet.

The Courier mail transfer agent (MTA) is an integrated mail/groupware server based on open commodity protocols, such as ESMTP, IMAP, POP3, LDAP, SSL, and HTTP. Courier provides ESMTP, IMAP, POP3, webmail, and mailing list services within a single, consistent, framework.
sSMTP is a simple MTA to deliver mail from a computer to a mail server. sSMTP is simple and lightweight, there are no daemons or anything hogging up CPU; Just sSMTP. Unlike Exim4, sSMTP does not receive mail, expand aliases, or manage a queue.
In the default mode, it transmits a mail to an SMTP server (for example at a free mail provider) which takes care of further delivery.
Configure SMTP e-mail in IIS when you want to deliver e-mail messages from your site. Mail can be delivered immediately or it can be delivered to a file location on disk where it can be retrieved for delivery later.




MailerQ is a high performance Mail Transfer Agent (MTA) and a very fast SMTP server, designed to deliver large volumes of email messages at very high speeds. MailerQ is based on RabbitMQ AMQP.

BulkMTA is Commercial Mail Server Similar to PowerMTA. IP Rotation, DKIM, Sender / Receiver Rate limiting.
EmailSuccess, an advanced SMTP Server (MTA) built from the ground up to handle the most critical reliability, performance, security, and deliverability requirements.



