Preserving Mails of 1 (one) account during provider switch using IMAP
I have a Thunderbird profile containing several mail accounts for several domains. Now I decided to switch for one domain the mail provider. I want to keep all mails for this account (and to move them to the new ISP's mail server). Beside the standard folders there are about 15 folders with topics. The account used IMAP and all information is downloaded to my PC. I can no longer access the mail at the old ISPs server, as the DNS already points to the new server.
I think if I only change the server settings for this account all my local messages get lost, as the messages are not yet available from the new ISPs server. So how can I transfer all those mail messages to the new ISPs server?
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you export them from Thunderbird using the export import tools add-on.
https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/
once exported they can be re-imported to a folder in local folders.
You can then move them slowly (500 mails at a time should be considered a absolute maximum. You might find you can not move that many) to the imap account so they synchronize with the mail server.
BE aware that IMAP is for synchronizing a few emails, it is not a file system where you can just drag thousands of items to a new location and expect it to "just work". For instance my new phone is still trying to synchronize my gmail account after weeks and it is doing the expected download, not the less used upload.
Thank you for this answer.
Is it normal, that I see in the original TB account (the one that will be discontinued) only 114 mails in the inbox, but ImportExportTools saves and restores 2357 email (the 114 emails represent the latest 114 mails received).
2357 is rather correct than 114... any explication for this?
I further have a big difference in Drafts (ImportExportTools shows every single version of drafts, while TB only shows the last version (I read elsewhere about this problem...)
The rest of my restored folders shows either the same count of emails or - astonishingly - one more than the original account...
P.S. Remember: ...I can no longer access the mail at the old ISPs server, as the DNS already points to the new server... Causes this probably the 114 tuncation in the inbox?
The number shown, as well as the details shown in Thunderbird are those from an MSF file index. Much smaller and faster to load than the full mbox which may by more than a few Gb in size.
Problems start to arise when the index and the mbox get out of sync, which may well be the case here. the mbox is what the import export tools use to export the mail. I actually doubt they use the MSF although I have never actually looked. It would be a simpler issue when exporting an MBOX to just copy the file when the destination format was also mbox.
The mbox format was a very common file format for mail once upon a time (just as EML was) and the export of the mbox is really for use in programs other than Thunderbird. so when the file is imported to Thunderbird a new MSF is generated. Hence I think the different. probably the result of issues with synchronization as the old account died.