For the small and medium sized companies looking for reliable mail server software on a tight budget, Mercury Mail Server is one of the options to go for. It is also one software that we recommend customer that would like to try implementing a low volume, small scale mail server without the high cost.

This software is free but it has an option to purchase documentations and/or support. In the author\'s own words - "Purchasing manuals or a support agreement are optional actions - you are not obliged to do so; but your support will ensure that the programs remain available as a viable option for all who need them."

Mercury is very robust, can take heavy workloads and works well on very minimal amount of memory. We have encounter a case where memory leak on a Windows NT Server causes it IIS, FTP and other programs to fail one by one but still Mercury runs without any problem.

The newer version (3.32) comes with 10 protocol modules but it is not necessary to install all of it. What is needed is probably MercuryX, SMTP Server, SMTP Client, POP3 Server, POP3 Client and POPPASS.

The SMTP server listens for connection on port 25 and accepts mails based on restrictions and policy specified by the server admin. It has also a powerful SPAM control feature of checking the connecting IP against a blacklist specified by the admin. This is done by doing a rDNS on the connecting IP address against a list of known spammers that are listed in a blacklist DNS server of SPAMCOP or some others.

Once it pass through, it will have to go through another list of checks that mostly only spammers would worry about like pure HTML mail format, mails without date, mails without subject, mails that are not MIME-compliant. Other than the last item, most options filters out mails that are send by spammers with their bulk mailer software. These software will connect to their target mail server and send the mail directly. It also issues different HELO command to diverse from a common method so as to aviod detection by spam filters. Last option enabled may filter out cc:Mail users, which has mail format that are not fully MIME-Compliant. There is also an option to block connection attempts from trouble makers if required.

The SMTP client basically delivers what is passed to them by the SMTP server. Not much configuration needed here.

Next is the POP3 server which listens on port 110 for connection from mail clients like their own Pegasus Mail, Outlook Express, Outlook or others. Upon proper authentication, the mails for the individual users will be released to them and deleted from the server.

The POP3 client is for collecting mails from other mailboxes in another server and transferring it into a user\'s mailbox. The POPPASS listens on non-standard port 106 for users to connect and change their passwords.

Mercury does not have a web server interface like some commercial mail servers plus it sometimes will not properly save your changes to the MERCURY.INI file.

Web mail function can be installed by enabling IIS & installing Squirrel Mail on the same server or on another web server.

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