loosing inbox-messages(provider-mailbox)

[europanorama]

i am using firefox and thunderbird almost all of the time. they are updated.
i have several mailboxes, among them the one from the provider. in thunderbird i can decide whether i will use this one or another. messages written from website are guided through this box.

i am using password-manager. i think someone is fishing my pass and deleting inbox-messages from time to time.

this happend before when changing that mailbox-adress or /and pass. actually i am using a unique password without manager. i will have to type it in every time. i will now observe if deleting has stopped definitely and report.

i was going through the security settings described here:(i have cablemodem)


http://www.wilderssecurity.com/showthread.php?t=50662
> in german only but higly interesting
http://www.trojaner-board.de/showthread.php?t=12154
http://www.ntsvcfg.de/#_intro
http://www.ntsvcfg.de/kss_w2k/kss_w2k.html#w2knetbios
tool mit lan(nicht manuell)
oder
http://www.dingens.org/
netzwerk

http://faq.underflow.de/#SECTION000110000000000000000
when i open thunderbird it says:
error sending pass-mailserver telling: login failed.
after waiting a bit until that popup disappeared i had to write a message logging in before sending(using no password-manager to be save). is this the standard precedure after changing the pass.
is this popup-message standard?