Junk mail flags do not remain set
Mail flagged as junk by my ISP is moved to Spam/Junk Mail folder. Some of the messages do not have the Spam/Junk flag set. I set them manually, then move to a different folder. When I come back to Spam/Junk the flags are cleared. This occurs only on some of the spam/junk mail not all.
What is the issue/problem and a fix. Seems like once a message is flagged as spam/junk the flag should not clear unless I do something.
Alla svar (2)
Is this a yahoo account? their spam filter is out of control and not opt out.
No, it is not a Yahoo account. Fastmail.
The problem only occurs accessing the mail account via Thunderbird. Some of the message that will not keep the Thunderbird spam flag are flagged by the ISP as spam others are not. Using other email applications, the problem does not occur. Accessing the account directly using a browser, all the email moved to the spam/junk mail folder by Fastmail remain there and the tags/flags are unchanged.