save email in TBP to reguler thunderbird

I have thunderbird email client on my PC in my home, but because internet connection in my home is very slowly, I use thunderbird portable (TBP) to download my new email in internet café, after than I want to put it in my PC. My question is if fist time I delete a new one in my TBP after copying to my PC, than I download again a new email, what should I can do?? (As far as I know, if I delete the old email on profile’s folder in my TBP than I copy to my PC, it will change profile TBP too. I mean after I get a new one and copy to my PC, I want to delete and get a new one again without leave the old one in my TBP).