As far as email messages go, this what IMAP is designed for. All your computers look at the same folder system and see the same messages. If by "email database" you mean address books, then that's a slightly different matter. Thunderbird's "email database" is its profile and possibly specific mail folders within that. You can try to put the whole profile on a shared drive, but users who do this often have issues. One thing to bear in mind is that there is a locking system that allows only one instance of Thunderbird to access the profile at any time. https://support.mozilla.org/en-US/kb/profiles-tb?esab=a&s=profiles&r=1&as=s You can also try moving specific email account folders to a shared location. This is found under '''[http://kb.mozillazine.org/Menu_differences_in_Windows,_Linux,_and_Mac Tools|Account Settings]|{select account}|Server Settings→Local Directory'''. I can't say I'm fond of this method, as it fragments your profile and makes ongoing maintenance more difficult. Pretty much all the online help I have ever seen assumes your profile is monolithic, and not scattered across multiple devices. I don't know how this works in conjunction with the file locking system. The only way I know to safely share address books between machines is to synchronize them to online resources.