Is your ISP also your email provider?

If so, you can't do this.

If OTOH your email address is independent of your ISP (e.g. It is with Gmail/Yahoo/Outlook etc) then you don't need to do anything. Those accounts don't care which ISP you use.

I am not familiar with "1x1" (did you mean "1&1") or iPage. Are these actually ISPs or might they just be Web hosts?

If it is your domain and you are able to keep the address, then you will need to set it up in Thunderbird to use the replacement server. You will lose access to the old server, so to be sure you really need to make your own local copies of messages in the old account.

IMAP vs POP matters because if your old account uses IMAP then your messages are actually stored on the server and you'll lose them when you switch servers. If the account was POP based then you do already have your own copy.

If both accounts use POP then it is possible that you could tweak the settings of the existing account and continue.

But if one is POP and the other IMAP, you cannot convert an existing account from one type to the other. Then answer is to set up a new account in Thunderbird.

Each email address is unique. So you cannot properly have the same email address concurrently at two different providers. So at some point you need to switch over and when you do so you need to be sure you have a secure copy of everything that matters that was stored in the old account. You could keep the dead POP account, but it will give errors when it cannot reach its server after your account is disabled.

The bottom line: copy everything that you want to keep into Local Folders in Thunderbird. Delete the old account, set it up anew with the new provider. This covers all the POP vs IMAP contingencies.

Thank you. Let me be more clear - Yes 1&1 and it IS POP. I AM moving both the domain and the email address that goes with it (email address that I'd like to keep) to iPage. I have the option to set up the new email account in iPage as POP - So, both the old and the new will be POP i.e there will NOT be any contingencies between IMAP & POP. And yes, off course I do not wish to keep the same email address on 2 servers! - So having said this, I am assuming we are going with this paragraph in your response: "If it is your domain and you are able to keep the address, then you will need to set it up in Thunderbird to use the replacement server. You will lose access to the old server, so to be sure you really need to make your own local copies of messages in the old account. " And if true, then Concerns & Questions: When you say "set it up" I can not set up a new one - remember the email is staying the same,So, it is already set up- so, I'd have to be able to edit he server settings of the existing email account in TB (1&1) to point to the new server (iPage) and in doing so I get into the Local Path issue which are exactly the 2 points I started with in my original post. Also - when you say: "you really need to make your own local copies of messages in the old account" HOW do I do this exactly? And if I have to restore the copies HOW would I do that? Thanks again.

In this special case where you switch from one POP-based provider to another, yes I think you could tweak the server settings at the right moment. At some point, the MX record for this account will be adjusted and the old server will become inaccessible in favour of the new server.

But I have never done this for live POP accounts, so to some extent I am hypothesising. However, I have done it with an IMAP cache moved into Local Folders, when my provider switched me to a different server. There I discovered that you can't paste message stores into an IMAP account using your file manager; when there is a disparity between the client and the server, the server wins. You have to add the messages to the client in such a way that it sees them as new arrivals and so posts them back to the server. So I copied the files to Local Folders, then moved them (in Thunderbird) to the my preferred place, in the live account's IMAP folders.

The bottom line is still to make an independent copy. Backing up your profile is easy to say, and certainly guarantees you an independent copy of all your past emails, but it isn't especially easy to use.

Copying all the messages you want to keep into your Local Folders account is another way to do it. Again that means the old messages are stored locally on your hard disk and safe from any catastrophes with live accounts. But this is tedious, and somewhat error prone, if you have a complex folder structure.

What I would do is open the profile and locate the files and folders which store the messages, and copy these. (This location is given in that Local Directory setting.) This leaves you safe to delete the old account, set it up against the new server and then paste back in all the folders, so you have a seamless transition with all your old messages transplanted into the new instance of your account. (To be pedantic, I would view this is a new account, even though it uses the same email address as before.)

Copying files and folders via your Operating System is almost always quicker and safe than doing it within the email client.

This last comment is almost certainly not relevant, but if you do copy message stores from account to to account, using your File Manager, you do need them to be using the same type of mail store. I am trialling maildir, so I can't copy maildir file stores over into the more conventional mailbox stores (or vice-versa). I'd have to do this within the email client, since it understands both systems and can convert between them.

Hi Zenos - Thank you. I have been working on this since my last post a few hours ago and it works but it's a lot of work! You do have do copy the folder when your files are - then RENAME the existing account to something like "old..." - Then create a brand new account with the same address - Then tell TB that the Local Directory is the directory you copied your files to, but TB will complain that this DIR is being used by your old account, but it gives you a brand new DIR to choose - which is where you should now copy the files to again - Then reboot & it will read the files - and then it works like a charm! I am gonna give it a few days and then delete my old account & the files that go with it (keeping at least one backup!) I think the MAIN reason it works like a charm is because of the POP to POP sync! - Anyway - thank you so much for your help. ps I found another bug with TB in this process. I'll have to post that one later...