Could not the other person just forward them to you? Forwarding as attachments would preserve the original messages, headers, attachments and all. Thunderbird can export messages as files. '''File|Save As''' allows them to be saved as text (. eml) files. Your mail client may be able to import this standard file format. If this is an ongoing requirement, it would be much better to set up the account in your own client yourself so you recieve these messages directly. Or set up a copy or forward action on the incoming server to pass them directly to you via an account that you use.