Bugzilla

I found way to duplicate the bug but haven't found a fix. 
Start with a fresh install of an account for a server that puts everything as a subfolder of Inbox as shown in comment 5, item "1."  This is default for dovecot, courier and cyrus.
Create a new folder under Inbox called archive. Don't create the folder Archives which is the default name, at least for en-US localization.
Go to Settings / Copies and Folders and select Other under archiving and with the folder "picker" choose folder Inbox/archive.
At the main screen, verify that archived messages get copied into Inbox/archive folder (or the year subfolder if that is wanted).
Now go the Setting / Server Setting / Advanced... and enter into Imap Server Directory just INBOX (uppercase, no trailing spaces). Click OK.
At main screen, select Inbox and then restart TB.
On startup, all folders should be at same level as Inbox (nothing now appears as subfolder of Inbox, but to the server they still are.
Now try to archive a message.
The infinite loop is visible in status bar. Just let it keep trying...
While it tries, go back to Setting / Copies and Folder and you will now see that archiving Other is still selected but it says "Choose folder...".
Choose folder archive (no longer shows as a subfolder of Inbox) from the list and restart TB.
After restart, archiving to the non-standard archive folder should work OK.

I don't think the problem occurs if you just stay with the default name Archives and don't choose Other but instead use the default selection ```Archives folder on:```.

I think the problem is caused by the preference ```mail.identity.idX.archive_folder```. The default setting looks like this example (with and without the imap directory set to INBOX):
```imap://gds%40tana.it@fwmail.tana.it/Archives```;  but when Other is selected the folder Inbox/archive is originally set, you see this:
```imap://gds%40tana.it@fwmail.tana.it/Inbox/archive``` which works OK as long at the Imap server directory setting is empty. But when imap server directory is set to INBOX, which "flattens" the paths, the URL is wrong until you fix it in the Other setting (or with config editor) so that it becomes
```imap://gds%40tana.it@fwmail.tana.it/archive``` (with no Inbox) and then the TB is no long confused when you try to archive a message into the "non-standard" named folder, e.g., archive.

So I think an easy workaround is to just go the Settings / Copies and Folders and make sure the Other selection for archiving is properly selecting the correct target folder for archiving. Then restart TB.

I found way to duplicate the bug but haven't found a fix. 
Start with a fresh install of an account for a server that puts everything as a subfolder of Inbox as shown in comment 5, item "1."  This is default for dovecot, courier and cyrus.
Create a new folder under Inbox called archive. Don't create the folder Archives which is the default name, at least for en-US localization.
Go to Settings / Copies and Folders and select Other under archiving and with the folder "picker" choose folder Inbox/archive.
At the main screen, verify that archived messages get copied into Inbox/archive folder (or the year subfolder if that is wanted).
Now go to the Setting / Server Setting / Advanced... and enter into Imap Server Directory just INBOX (uppercase, no trailing spaces). Click OK.
At main screen, select Inbox and then restart TB.
On startup, all folders should be at same level as Inbox (nothing now appears as subfolder of Inbox, but to the server they still are.
Now try to archive a message.
The infinite loop is visible in status bar. Just let it keep trying...
While it tries, go back to Setting / Copies and Folder and you will now see that archiving Other is still selected but it says "Choose folder...".
Choose folder archive (no longer shows as a subfolder of Inbox) from the list and restart TB.
After restart, archiving to the non-standard archive folder should work OK.

I don't think the problem occurs if you just stay with the default name Archives and don't choose Other but instead use the default selection ```Archives folder on:```.

I think the problem is caused by the preference ```mail.identity.idX.archive_folder```. The default setting looks like this example (with and without the imap directory set to INBOX):
```imap://gds%40tana.it@fwmail.tana.it/Archives```;  but when Other is selected the folder Inbox/archive is originally set, you see this:
```imap://gds%40tana.it@fwmail.tana.it/Inbox/archive``` which works OK as long at the Imap server directory setting is empty. But when imap server directory is set to INBOX, which "flattens" the paths, the URL is wrong until you fix it in the Other setting (or with config editor) so that it becomes
```imap://gds%40tana.it@fwmail.tana.it/archive``` (with no Inbox) and then the TB is no long confused when you try to archive a message into the "non-standard" named folder, e.g., archive.

So I think an easy workaround when the "infinite loop" occurs is to just go to the Settings / Copies and Folders and make sure the Other selection for archiving is properly selecting the correct target folder for archiving. Then restart TB.

I found way to duplicate the bug but haven't found a fix. 
Start with a fresh install of an account for a server that puts everything as a subfolder of Inbox as shown in comment 5, item "1."  This is default for dovecot, courier and cyrus.
Create a new folder under Inbox called archive. Don't create the folder Archives which is the default name, at least for en-US localization.
Go to Settings / Copies and Folders and select Other under archiving and with the folder "picker" choose folder Inbox/archive.
At the main screen, verify that archived messages get copied into Inbox/archive folder (or the year subfolder if that is wanted).
Now go to the Setting / Server Setting / Advanced... and enter into Imap Server Directory just INBOX (uppercase, no trailing spaces). Click OK.
At main screen, select Inbox and then restart TB.
On startup, all folders should be at same level as Inbox (nothing now appears as subfolder of Inbox, but to the server they still are).
Now try to archive a message.
The infinite loop is visible in status bar. Just let it keep trying...
While it tries, go back to Settings / Copies and Folder and you will now see that archiving Other is still selected but it says "Choose folder...".
Choose the folder "archive" (now the same level as Inbox) from the list and restart TB.
After restart, archiving to the non-standard "archive" folder should work OK.

I don't think the problem occurs if you just stay with the default name Archives and don't choose Other but instead use the default selection ```Archives folder on:```.

I think the problem is caused by the preference ```mail.identity.idX.archive_folder```. The default setting looks like this example (with and without the imap directory set to INBOX):
```imap://gds%40tana.it@fwmail.tana.it/Archives```;  but when Other is selected the folder Inbox/archive is originally set, you see this:
```imap://gds%40tana.it@fwmail.tana.it/Inbox/archive``` which works OK as long at the Imap server directory setting is empty. But when imap server directory is set to INBOX, which "flattens" the paths, the URL is wrong until you fix it in the Other setting (or maybe also with config editor?) so that it becomes
```imap://gds%40tana.it@fwmail.tana.it/archive``` (with no Inbox) and then the TB is no long confused when you try to archive a message into the "non-standard" named folder, e.g., archive.

So I think an easy workaround when the "infinite loop" occurs is to just go to the Settings / Copies and Folders and make sure the Other selection for archiving is properly selecting the correct target folder for archiving (Inbox must not be in the path). Then restart TB.