My users are using outlook 2003 with exchange 2003.All the users use pop3 to get mail from outside providers. They also have configured the option leaving the mail in the pop3 server.The mail is delivered to the exchange mailbox, not a PST.Recently the users receive all the messages that are in the pop3 server, again and again, creating duplicates on theirs mailbox.Some users also complain that some messages have disapeared.I got a lot of errros 9555 in the aplication log of the exchange server.The only recent change in the network configuration was the installation of AVG anti-virus in all the machines, including server.Can someone help me with this problems?

Your POP3 problem has nothing to do with Event ID 9555.KB 885870 addresses your duplicate email issue when using POP3. http://support.microsoft.com/kb/885870Event ID 9555 is addressed in KB 904945. It is safe to ignore this event.http://support.microsoft.com/kb/904945Bhargav Shukla - MSFT - Exchange Reference: Exchange Server 2007 TechCenter - http://technet.microsoft.com/en-us/library/bb124558.aspx; Exchange Server 2003 TechCenter - http://technet.microsoft.com/en-us/library/bb123872(EXCHG.65).aspx; Microsoft Exchange Team Blog - http://msexchangeteam.com/default.aspx