In Gmail All Mail is just that. Even Deleted. When you delete a message in an email client Gmail removes the tag, in your case the Inbox tag, and keeps a copy in All Mail. I do not remember if you can log into Gmail directly and change that. You might look.

If you use Thunderbird to delete items out of All Mail folder, they get deleted. but if you use the retention policy to delete items out of the all mail folder, they dont. You would think that applying the retention policy to the All Mail folder/label in ThunderBird would work but it does not. I am not sure why. Afterall, it appears that you are manually able to delete stuff out of All Mail. In any case, I will log into to Gmail and poke aground to see if there is a setting I can change that might help.

Why do you feel a need to have All Mail visible in Thunderbird? Or is this more a concern about managing what is left on google's servers?

The latter. Thanks for asking.

Any email I select to delete is moved to gmail imap Bin/Trash folder; this is specified in Account Settings. If I empty the gmail imap Bin/Trash folder and then compact that folder, when I logon to gmail webmail, those emails have been deleted from the 'All Mail' folder.

If I delete an email by a method where it is not moved to the gmail imap Bin/Trash folder, then it will remove/delete the label and therefore remove from the folder it was in eg: Inbox, but because it was not actually moved to the gmail imap Bin/Trash folder then it cannot be deleted from 'All Mail'.

When you use the retention policy options on eg: Inbox to delete emails older than xx, do those deleted emails go to the gmail imap Bin/Trash folder? I do not use the retention policy method, but...and I'm thinking out aloud here....as gmail has it's own quirky methodology....that the retention policy method does not put them in the gmail trash bin and only removes a label hence why those emails are still in 'All Mail'. This may also explain why you are trying to have a retention policy on the 'All Mail' folder. I suspect that you cannot simply remove the 'All Mail' label, those emails have to be put in the gmail trash bin, hence why the manual method works and retention policy doesn't.

So if the intention is to remove a label from an email, but not delete from 'All Mail' so keeping as an 'Archive' then the 'Retention Policy' method is perfect.

To remove emails from 'All Mail' perhaps this may fix the issue. Create a Message filter for the gmail email address/mail account which you could set up to operate only when manually run; where it matches Age in Days is greater than XX to perform an action to move message to the gmail account trash/bin folder.

Select that filter Then you can choose: 'Run selected filters on : 'All Mail' on gmail mail account'. click on 'Run Now'. uncheck the filter to disable, but keep filter for another day.

I have been reading things that lead me to believe what your saying is good to go, but here is the question; shouldn't the retention policy place the item into the trash? I am not sure what ThunderBird is doing on the back end with the retention policy kicks in on GMAIL IMAP.

The other thing I am not sure of is where the emails go from the inbox after they have been affected by the retention policy. I have not seen them in the trash folder, but they still reside in the all mail folder / label.

Shouldn’t Thunderbird apply the retention policy directly to the AllMail folder / Label if you set it so. The thing is that it (the retention policy) does not appear to affect any messages in the AllMail folder/ Label. Even when specifically applied by folder. Also there is no way that I know of to specify to Thunderbird what the retention policy does with mail; meaning, is it possible to configure ThunderBird to remove the current label (ie INBOX) and put it into the delete trash folder (ie bin/trash) then empty trash on exit?

Thanks for the suggestion for the manual email rule work-around, but I was hoping to get a more automated solution. As an aside, I been doing shift+click (multi-highlight), and shift + del for a work-around.

In pursuit of figuring this out, I changed the archive option in Thunderbird to None thinking it would not pass emails to the all mail folder. I will see if that affects anything, but for not I haven't noticed a difference.

There is another thing I notice: Upon startup, when Thunderbird appears to be working its retention policy, an error shows up in the activity Manager (Tools Menu → Activity Manager). The error indicates a “NONEXISTENT” code for the “[Gmail]^All Mail (Failure).”

I bet because GMAIL IMAP All Mail folder is not really a folder, Thunderbird is unable to process the retention policy for it, and errors out. It looks like that there is no way to apply a Thunderbird email retention policy to the AllMail folder / Label on a Gmail IMAP account. So, unless manually delete items from the all mail folder, emails will stay on the Gmail server indefinitely, retention policy be darned, (until you manually remove them). This is turning out to be a bummer.