K9 is an opensource email client based on the Email application shipped with the initial release of Android. K9 is focused on making it easy to chew through large volumes of email. It's our hope that K9 leads to improvements in the core Android mail client.
DKIMproxy is an SMTP-proxy that signs and/or verifies emails, using the Mail::DKIM module. It is designed for Postfix, but should work with any mail server. It comprises two separate proxies, an "outbound" proxy for signing outgoing email, and an "inbound" proxy for verifying signatures of incoming email. With Postfix, the proxies can operate as either Before-Queue or After-Queue content filters.
Dawn will convert your address book from one program's format to another.
Tool Sammlung zu mbox Email Dateiformat - teilweise windows
Tips für Postfix, wenn er zuviele Anfragen bekommt und die Abarbeitung zu lange dauert