Both versions of Mercury are highly modular, allowing support for different sets of Internet protocols to be installed as required.

Mercury was originally developed to handle mail, both internal and external, on Netware servers in either bindery or NDS mode; Mercury ran on the system server, and integrated with Pegasus mail running on MS-DOS or Windows workstations.

[2] Mercury is extremely standards-compliant, supporting all major Internet mail-related protocols including SMTP (for both sending and receiving mail), POP3 and IMAP.

The relay control is very effective, and the ability to filter mails based in many rules, making it very efficient.

Mercury/32, while not open source software, can be extended by anyone as the development documentation is free and publicly available at the pmail community.

)[6] On 19 June 2009 David Harris announced on the Pegasus Mail site that all development of Pegasus Mail and the associated Mercury program could only continue if sufficient users would commit to donating US$50 annually;[7] on 21 July 2009 he said that there had been a good start.

[9] On 25 December 2019 he said that, while there has been a delay due to health issues, he "can only promise you that there is progress, and that [he is] totally committed to getting these new versions released" and he is working, among others, on support for OAuth2 and OpenSSL v 1.1.1 and he expects "to have builds of Mercury v5 available to testers and interested users in the first three months of the New Year".

[10] The XAMPP is an initiative by Apache Friends to develop a cross-platform web server solution pack with the main core components of the Apache HTTP Server, MariaDB or MySQL database and the PHP and perl interpreters,[11] intended to be a cross platform equivalent of the LAMP stack used on Linux.