Email? Use IMAP. Your current POP-based service is fundamentally unsuited to your needs. Contacts are not so easy. You need a common central data store that all your installed address books can synchronize with. Google Contacts is one such, but there are difficulties in that it and Thunderbird handle street addresses differently. I use gContactSync to synchronize Thunderbird with Google and for the most parts it's quite satisfactory. Where I have trouble is with a Blackberry, but the Blackberry phone has various other issues that lead me to think that Blackberry coding is not of the highest quality. Another (and non-google) solution is this add-on: https://addons.mozilla.org/en-US/thunderbird/addon/addressbooks-synchronizer/ which can sync your address books to a variety of different resources, including a folder in an email account. So this is fine between various installations of Thunderbird, but probably can't reach out to other devices or email clients. I haven't tried it with an ftp server yet; if you are able to run your own then this may offer the best way of using this add-on. I think a cause for concern is that Thunderbird's Address Book use a "flat file" format, where each address book is stored within a single file. So one small minor change to one Contact potentially necessitates the whole file (address book) being updated, leading to large and therefore slow transfers between Thunderbird and the relevant server.