OpenSMTPD is described as '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' and is an app in the office & productivity category. There are more than 10 alternatives to OpenSMTPD for a variety of platforms, including Linux, Mac, Windows, BSD and Self-Hosted apps. The best OpenSMTPD alternative is Postfix, which is both free and Open Source. Other great apps like OpenSMTPD are Haraka, Exim, Sendmail and Courier-MTA.
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.
Postfix is the most popular Mac & Linux alternative to OpenSMTPD.
Postfix is the most popular Open Source & free alternative to OpenSMTPD.
Haraka is an open source SMTP server written in Node.js which provides extremely high performance coupled with a flexible plugin system allowing Javascript programmers full access to change the behaviour of the server.
Haraka is the most popular Self-Hosted alternative to OpenSMTPD.
Exim is a message transfer agent (MTA) developed at the University of Cambridge for use on Unix systems connected to the Internet.
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.
A small Mail Transport Agent (MTA), designed for home and office use. Part of DragonFly BSD , it accepts mails from locally installed Mail User Agents (MUA) and delivers the mails either locally or to a remote destination.
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.
Microsoft SMTP Server is the most popular Windows alternative to OpenSMTPD.
Microsoft SMTP Server is the most popular commercial alternative to OpenSMTPD.
Inbucket is an email testing application; it will accept messages for any email address and make them available to view via a web interface.
NikaMail is a 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.
A lightweight mail server with SMTP and POP3 support. It mainly used as store-and-forward mail server with POP access to spooled messages or it can be used as a personal internet mail server.
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