I have 2 email accounts with k.st. These are historical and paid for accounts and at the end of last year I had a spam problem with one of those accounts. Basically, someone had used my account to send loads of spam out. I resolved that issue with k.st support and a password change to a more complex, robust combination of letter/numbers/symbols.
However, I stopped receiving copies of emails in Outlook 2010, but only with one of the accounts. For the sake of demonstration I'll call the accounts z1@k.st and z2@k.st
Issue:
When sending an email from either outlook or from k.st web based email, k.st will receive and send emails from both the z1@k.st and z2@k.st addresses without any problem. However, only the emails from z1@k.st will appear in the Outlook inbox. Emails from z2@k.st show up as downloading in the progress monitor of Outlook, but once downloaded they will disappear, as if permanently deleted.
I have done tests from both Outlook and web-email, from both accounts, sending mail to both accounts and a gmail.com account. In all cases, when logging online, the emails are shown in all three accounts inboxes. When then doing a Send/Receive from Outlook, all emails from z1@k.st are downloaded. All emails from z2@k.st appear to be downloaded into each account, but then disappear once the download has completed.
To add to the conundrum, I get an occasional spam message with the header From: z2@k.st To:z2@k.st but the header shows that this has come from a server in Afghanistan. For whatever reason, Outlook accepts these mails but puts them in my Junk Email box.


I've checked that there are no rules that have been created to automatically delete emails from z2@k.st and I have created an account in my contacts list for z2@k.st, which I understand should then ensure emails from that email are accepted. It has made no difference.
I'm out of ideas. Can anybody help me to resolve this problem?