Accessing your mail from other computers
From MozillaZine Knowledge Base
Thunderbird is just a email client, not a email service or email provider.
The simplest way to access mail when you're away from your computer is to use webmail. That is use your browser to read/send messages using a web page provided by your email provider. Normally you'd only be able to access new messages if you did this. However, if your email provider also provides a POP server you can configure Thunderbird to leave a copy of messages on the POP3 server using Tools -> Account Settings -> Server Settings -> "leave messages on server". That will let you access the messages from both Thunderbird and webmail. You should enable Tools -> Account Settings -> Server Settings -> "for at most X days" to avoid filling up your mailbox.
If you have several accounts you might consider using a free service that lets you access webmail and/or POP and IMAP servers from a browser. They're typically supported by advertising. Be sure to read their privacy statements beforehand and find out whether they can make a secure connection to your mail server.
Several startups let you access all of your email accounts from a web page but their focus is on integrating multiple sources of communication so they may also support instant messaging, social networks, SMS etc. from the same web page.
If you're going on a trip and want to access some of the messages stored on your hard disk its possible to put them back in your mailbox without making them look like they're forwarded.
You can store your profile (and Thunderbird) on a USB drive and use it on another computer if you have access to a USB port. This is especially usefull for roving users who don't always use the same group of computers. Public computers (such as those in libraries) typically don't provide access to a USB port.
If the other computer is on the same network you could store your profile on a file share and access it from either computer. You'd need to follow the instructions for moving your profile on the other computer to tell Thunderbird where the profile is stored. You can't just drop it into the default location and expect Thunderbird to discover and use it.
If you have a IMAP account you can store your messages in remote folders and access them as if they're in local folders. This means you could use any email client that supports IMAP and access all of your mail. You wouldn't be able to access your address books. However, you could export them as .CSV or .LDIF files and import them in the email client on the other computer.
If your email provider doesn't support IMAP one workaround would be to sign up for a free IMAP account at Gmail, and configure the optional Mail Fetcher to automatically fetch mail from your POP server and merge it into the Gmail webmail inbox. You can configure it to either keep a message on the POP server or delete it, when it periodically fetches it. That way you could read mail from your POP accounts on a different PC using a Gmail IMAP account in Thunderbird. If you define the POP accounts email address as a multiple identity you could even send mail from the Gmail account using that email address.
Remote access to your computer
You could install some sort of password protected server to provide remote access to your PC using a client. VNC is one possible solution. Its a good idea to tunnel VNC through SSH for better security. If you're using a firewall you need to configure it to allow remote access via the VNC client. There are free web based VNC viewers such as s-code if you can't install a VNC client on the other computer, though they offer less functionality.
Comodo EasyVPN provides a way to group multiple PCs into a secure peer to peer network over the Internet. They claim it can be setup in minutes and provides 'remote desktop' control over other computers on the VPN.