TB doesn't delete mail from server at set nr of days(Linux)

[unkl]

i have set thunderbird in pop3 configuration to leave the mail on the server and delete it after 90 days. there is still mail on the server over a year old and thunderbird does not delete it. i set up another instance on debian to see if this was a windows related bug, but still the same problem. thunderbird does not delete the mail from the server. is there a limit on the number of days? like in old windows mail client the limit was 60 days, but it would default to 60 days if you try to set a bigger number, thunderbird accepts 90 days but does nothing. this is for more than one account on different web-hosts and different domains.

[DanRaisch]

Were those messages downloaded to Thunderbird before you set that deletion period value?
Who is the provider?