Using Exchange Server 2010 and configured POP3. When using Outlook express POP3 to download mail i get error "Message number 1 could not be retrieved. Account: xxxxx Server : 192.168.1.13 Protocol POP3, Server Response: 'ERR Server Unavailable 21', port 110, secure(SSL):No, Server Error 0x800CCC90, Error Number: 0x800420CD" Checked the tick mark in advanced tab "This Server requires a secure SSL Connection " telnet to pop3 port 110 is successfull

Hi, Maybe you could try below: 1 Make sure no firewall affect your Exchange server. 2 Verify that whether there's any corrupt mail in your mailbox, if you have delete it. 3 Reset the Outlook Express message rules: a. Start Outlook Express. b. On the Tools menu, click Message Rules, and then click Mail. c. Under Select the Conditions for your rule, scroll down and select the Where the message size is more than size check box. d. Under Where the message size is more than, click the size. e. Under Rule Description, select the check box for the value that you want to edit. f. In the Set Size text box, type 1000, and then click OK. g. Under Select the Actions for your rule, select the Delete it check box, and then click OK. h. Close Outlook Express, and then restart the program. Best Regards!

This is the screen shot of the error. Unable to download the message.

Thanks for the info. This did not work. I tried in outlook i get the error.

Sorry to bump an old thread, but how is this possibly an answer? How can the ISP have anything to do with it? The IP of the server he's attempting to contact is a local one. The error message clearly says the server has reported an internal error. I am having the same problem - Exchange 2010, users with domain accounts can send and receive perfectly, but others who use POP3 can't get their email or send. Send and receive connectors, routing rules, firewalls, etc are all fine, as the correctly working domain clients demonstrate. I can't for the life of me find a reference to a valid technical solution. I see elsewhere there's an issue relating to the server cutting off the connection, which was resolved by rollup 2 - well this one has rollup 6 so I presume it's all right. I saw elsewhere a compliance DLL issue - I have added the compliance lines to the pop3.exe config file. Those are the only things I've seen. I'm new to Exchange admin so any help with this would be great!