America Online was a suite of software to get the most out of your AOL internet account. This is the first Mac version, in 1989.  It allowed you to compose, send and receive emails.  

America Online v2.6 from 1995.  Came with their first browser version 1.0 allowing FTP, Gopher and web (HTTP) online browsing.  

Eudora was probably the most popular email client in the early 90's.  This first release of Eudora supports POP and SMTP. See also: Other releases of Eudora  

EIMS is Eudora's POP3 and SMTP mail server for Macintosh, fully fledged with accounts config, memory threshold config, console capturing, etc...  

Eudora Light v1.5.4 for 68K and PPC Macs.  Version française.  

Eudora Pro 2 is a full featured email client.  It supports automatic binhex, apple single and apple double attachments, signatures and more.  

Eudora Pro v3.1.1

FirstClass 2.5 suite includes the client, the server and the forms editor.  

Green Mail is a fully 68K compatible email client.  It's loaded with features, yet only weights 2MB and it has a very nice interface fully embellished with stylish color icons.  

LetterRip Pro server version 3.0.7 containing both the server app and the administration app.  

MacMail is a simple program designed to convert a unix-style mail file to a series of text files usable on Macintosh.  Each message is written to a file, with the letter's subject becoming its file name.  See the about window for...

Mulberry is an email client that has a large number of features and can work with sending and receiving via Gmail (as of 2017). Email could break when Google completely sunsets SSLv3/TLSv1 support for email. Receiving email works over SSLv3,...

POPMail II v2.2 is an email client for earlier 68K Macintoshes.