Can't limit number of emails stored on phone
1. I want Thunderbird to automatically erase all but the most recent 250 on my phone as it downloads new ones from my server. As it does so, I do not want the downloaded messages marked as "read" on my server, nor do I want messages erased on my phone to be deleted from my server. (That is all to be taken care of by my desktop email program.)
Phone: Moto g power 5G - 2024; OS: Android 15; Thunderbird v: 23.0 Settings: Fetching mail - Local folder size: 250 messages - Sync server deletions: Off - Mark as read when deleted: Off When I delete a message: Do not delete on server - Erase deleted messages on server: Manually
At present, Thunderbird downloads all the incoming messages and leaves them on, so I quickly find I have 1000+ messages stored on my phone. This eventually slows it's performance notably. I have to manually erase the messages, and then empty the trash, in order to circumvent this problem.
Also, when my desktop downloads the email, many of them are now marked read, even though I haven't read them. I am wondering if Thunderbird for Android isn't marking some or all emails as read on my server as it downloads them to my phone?
Opaite Mbohovái (1)
I'm assuming your using pop protocol to some degree or a mix across devices.
On your read status question, have you also unticked "mark as read when opened" from TB-A settings > account name > reading mail. This could be the reason for some emails showing as read on your desktop.
The app doesn't support any auto deletion or setting to maintain a rolling fixed number of emails
You can raise this as a feature suggestion on Mozilla connect where the community can vote for it.
There has been requests from the community for filtering capability. Perhaps a rule based filter could have some overlap with your own needs if developed.
https://connect.mozilla.org/t5/ideas/filtering-with-android-thunderbird/idi-p/61144