Issue Webmail - sth opens emails on server

[hubert]

Dear friends, a friend of mine co worker has a problem. When a new mail is coming, it's closed for 15-20 minutes and then after this time the mail opens - like it is read, but nobody reads it. She does not read it on any other client - only webmail. Its been like this since last Tuesday. Before everything had been as it should - the message was closed till read. Now its closed for 15-20 minutes and then it opens itself. Please Can You suggest any thing I can do to fix it.

Regards, Hubert