Under both Windows 7 Thunderbird 101.0b9 (32-bit) pop and imap all messages from the previous day are being deleted from my inbox on all systems accessing my e-mail account. I have previously been running pop when this event started about 3 weeks ago. On the advice of my internet provider who said they investigated my mail account I converted to IMAP. I receive mail on my cell phone, an IMAP laptop and my IMAP desktop. The laptop and desktop are windows 7. The lap top and cell phone are set to never delete. My desktop is set to move deletes to trash and to never delete. If I move all the mail that has accumulated overnight from my laptop to a local folder, it is retained there even when the mail on my desktop disappears. If I do not and the mail spontaneously disappears, it is gone from all devices. If this appears to be a beta related problem, I would be happy to leave the beta system if it did not entail reinstalling Thunderbird. In the meantime, I will refrain from updating beta unless it is a solution to my problem.