Mozilla Thunderbird

[#1]

I have been using Mozilla Thunderbird for some time. I used to use Outlook Express without problem, until a friend started sending me e-mails with attachments that were too large for OE. Thunderbird handles them with ease. I also use Mailwasher so that I can check incoming e-mails before I get them on my pc.
I have two e-mail accounts, the usual "postmaster", and another which I use as a way to protect myself a bit from spam, etc - I only give my personal account to friends. Until now, these two accounts have been separate in Thunderbird, in that I have the standard Thunderbird Local Folders, plus both of the two accounts. All incoming postmaster e-mails came into the Thunderbird postmaster "In" box, and all "friends" e-mails came into the Thunderbird friends "In" box. This worked, but I would prefer to have both sets of e-mails coming into one "In" box, and all outgoing went into one "Sent" box.
I managed to change things so that all outgoing e-mails now go via the Local Folders "Sent" box, but have not had any success changing things so that both my received e-mail accounts come into the Local Folders "In" box. Just to aggravate the situation, I have managed to lose my Thunderbird "postmaster" account.
I want to add that Mailwasher is working properly, so it isn't MW causing the problem.
I would appreciate some guidance, please
Thanks

[#2]

Not a thunderbird user but could you not set-up a mail rule to copy any received emails from your friends mailbox to your common mailbox older? I know you can set-up rules for moving/tagging incoming mail but can't explain how as I don't have it installed. Maybe a google search will help.

[#3]

Thanks, Peter, for your reply. I seem to have found the answer - well, more like fell on it. I'm not sure how to explain it, so there may be things I didn't need to do, but it was something like this:-
1. Save any e-mails you need to keep;
2. Delete the contents of the list of "personal" and "postmaster" accounts that show the In Tray and the Sent Tray for each - if you understand what I am trying to say;
3. Go to "Accounts Settings", which should show both of the accounts I had set up;
4. Select the "postmaster" account, and when the window opens select "Advanced";
5. There is a short list of what to do with e-mails from the POP3 server - select "Local Folder", and close that window;
6. Repeat 4 and 5 for the "personal" account.
That seems to have got the incoming e-mails for both accounts going into the Local Folders In Tray.
I haven't tested for replies to e-mails that were addressed  to"personal" or "postmaster" to confirm that (a) the replies go, and (b) the replies use the Local Folders Sent Tray. Fingers crossed.
Thanks