KMail mail check failure

in the last 6-8 months I have been having occasional failure of mail check both interval and manual. The symptom is the bottom right progress bar shows constant movement with no percentage given and no new mail.Workaround is close kmail, reopen it go to Settings - Configure Mail - Accounts - Receiving - Modify - Apply (without editing anything) - OK and it downloads and will do so for 1~30 days and the same thing happens again. Doesn't matter which of 4 POP3 accounts I select to (not) modify - all then download Just open/close does not fix it nor TDE exit/new session or reboot. Machine normally runs 24/7 Has persisted through a complete machine replacement (with the same ~.trinity/share/apps/kmail/mail directory and filters This is with KMail 1.9.10 (enterprise35.0.20100827.1168748) (Using Trinity 3.5.13.2) on Debian 7 reported by synaptic as kmail-trinity 4.3.5.13.2-0debiian7.0.0+0. The same setup had been working fine for some months beforehand Any ideas ? Regards John Campbell