Mail grew out of NeXTMail, which was originally developed by NeXT as part of its NeXTSTEP operating system, after Apple's acquisition of NeXT in 1997.

Mail was originally developed by NeXT as NeXTMail, the email application for its NeXTSTEP operating system.

It supported rich text formatting with images and voice messaging, and MIME emails.

When Apple began to adapt NeXTSTEP to become Mac OS X, both the operating system and the application went through various stages as it was developed.

In a beta version (codenamed "Rhapsody") and various other early pre-releases of Mac OS X, Mail was known as MailViewer.

In addition, it offered notes and to-dos (which could be synced with iCal) as well as a built-in RSS reader.

Mac OS X Snow Leopard (version 10.6) brought Microsoft Exchange Server 2007 support.

Also added was the capability to group messages by subject in a similar fashion to Mail on iOS 4.

In OS X Mountain Lion (version 10.8), Mail received VIP tagging, Safari-style inline search for words within an email message, the ability to sync with iCloud and new sharing features.

In macOS Big Sur, Mail was updated alongside the other first-party apps to feature the new design language of Big Sur, with a full-height sidebar and updated icons that match the blue color of the app's icon.