Qiqqa
Mendeley
Zotero
JabRef
Citavi
Docear
Paperpile
BibDesk
MailStore
Cryoserver
Gmvault
imapsync
Intradyn Email Archiver
Hornetsecurity Email Archiving
Mail Backup X
Piler
Qiqqa MailStoreQiqqa is by far the strongest solution for research and managing pdf's. Zotero, named as a comparison is weak as it does not allow pdf;s to be loaded into its interface - you need to use a pdf reader, which defeats its whole purpose. With Qiqqa documents in a library can be searched together. It has excellent maps of your libraries. It is not prefect, having a few glitches, but still is the only one of its kind.
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Cryoserver - Cryoserver is an all-in-one email archiving solution that empowers you to preserve your email in a tamper-evident archive, making you transform your data into a useful archive for everyday use.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Gmvault - Backup the emails in your Gmail account.
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .
imapsync - Console-based utility for migrating IMAP mailboxes.