give replay to rsolve issue

This seems rather a confused question. You're asking how to copy or transfer messages from one ''computer ''to another without losing track of whom it was sent by. In general re-sending them via email is best avoided. Re-sending them as attachments would preserve their contents, but attached messages are not easy to work with. When you ask to send to a different PC, does this also mean to a different email account? If you use IMAP on both of your computers, then the messages are stored on a server. So each attached computer will display the same set of messages, since those messages are stored on a server and will be displayed on any attached computer using an email client that connects using IMAP. So you don't need to actually so anything to share these messages. If you want to copy them to another account, via email, then look for the Mail Redirect add-on. This lets you send a message in a way so that it appears to the recipient to have been sent from the original sender, rather than from you, as would happen if you used "forward", "reply" or "edit as new". But any form of forwarding via email is less efficient than moving messages between accounts. I would have thought IMAP is a good fit to your needs, if I have understood what you're trying to do. https://addons.mozilla.org/en-US/thunderbird/addon/mailredirect/ A downside of Mail Redirect is that it doesn't show up as a filter action, so it isn't immediately obvious how to use Mail Redirect in a filter. I do seem to recall that I found an add-on that allowed Mail Redirect to be used in a filter, but right now I don't have any record of how that was done. :-( But, my usual reply to anyone looking at automated forwarding would be to look at what can be done at the server. If a server forwards messages form one account to another, it looks very much as if the message was sent to the final recipient form the original sender, with no obvious sign of it having been handled by an intermediate server. I don't know if this is relevant to you, because we don't know if the "external" pc is using the same account or some different account. Forwarding at the server isn't of much help if all these computers are using the same email account.