K-9 Mail Android is an open source client for Android e-mail with multi-directory synchronization, email signatures, BCC-in-itself, the return address configuration, keyboard shortcuts, support Exchange, the signaling message, IMAP, delete, save attachments, notifications and much more configurable.
Android App E-K9 is one of the best email client for Android. It is loaded with all the email features you might think, except ActiveSync (push e-mail, IMAP, however, the integration synchronizes almost as fast as ActiveSync). By far the best alternative to the default mail client created by Google.
I personally like the synchronization of IMAP folders, signatures, and the ability to multi-manage multiple email accounts from a mobile device. The list of features is huge – from personal configuration of IMAP and POP3 protocols, to custom set of keyboard shortcuts.
Once you have IMAP, POP3, and / or WebDAV (Exchange) accounts, everything else is typical of a mobile email client. Be sure to set your mail preferences, such as notifications and synchronization options. K9 usability benefit Mail has over Gmail is the Back / Forward buttons, which makes navigating through e-mails from the practice of sending a message, then return to the list each time.
The user interface has recently added the option of conventional light or dark background. Flu Warning: When you see a list of mail in landscape mode (keyboard open), the electronic elements are very small, it can be difficult to read small fonts.