These errors occur whilst VPOP3 is communicating with your ISP's POP3 mail server to retrieve your mail.

If the message text is

Error with Pop3 Client (XXXX (YY))
The server connection was closed unexpectedly

Then this means that the the connection between VPOP3 and your ISP's POP3 mail server was closed when VPOP3 did not expect it to be. This can be caused by the network connection failing or a bug in the ISP's mail server which drops the connection in abnormal circumstances.

Following this text there should be a further description of the specific error which occurred. See here for a description of those errors.

If the message text is

The VPOP3 POP3 Client (XXXX (YY)) has encountered an error whilst retrieving messages from your ISP POP3 server
The received error was: "ZZZZZ"
The last command sent by VPOP3 was: "WWWWWWWW" 

This means that your ISP's POP3 mail server returned an unexpected error response when VPOP3 sent a command. 95% of the time these errors are caused by problems with, or bugs in, your ISP's mail server, so we recommend that you contact your ISP if the situation is not mentioned below.

• If the last command sent by VPOP3 was “*ENV xxx”, then this is probably because you have told VPOP3 to use Demon POP3 extensions, but your ISP does not support them (most don't), so go to the In Mail page in VPOP3, press the Routing button and disable the Use Demon POP3 Extensions option.
• If the last command sent by VPOP3 was “USER”, then this can mean that you have mistakenly created a second In Mail configuration in VPOP3. Go to the In Mail page, then, using the Svr: drop-down list, choose the second or later entry and find the one which does not have a User Id: entry, then press the Remove button to remove that entry.
• If the received error is something like “-ERR Invalid Login” then check the username and/or password on the VPOP3 'In Mail' tab. Check this with your ISP. In all cases, this error is coming from your ISP, so the details you have entered, don't match what your ISP have told you to enter.

If the message text is

VPOP3 was unable to make a temporary message file for receiving
incoming POP3 mail. The POP3 collection session was terminated
prematurely. Windows reported error 32 when VPOP3 tried to create
POPIN.TMP in the VPOP3 directory

This means that another program is accessing the POPIN.TMP file when VPOP3 needs to access it (Windows error 32 means that another program is using a file). That other program might be a virus scanner, backup program, or, in rare cases, another running instance of VPOP3.

If the message text is like:

The VPOP3 POP3 Client "Maru"(0) Encountered a file error opening the UIDL storage file.
Error Code - x The file has not been read, and you may receive duplicated messages as a result of this.
Please contact your dealer and inform them of this message.

The UIDL storage file is a file where VPOP3 stores a list of which messages it has previously downloaded (v4 and earlier). This error means that VPOP3 couldn't read that file, so it could not see which messages it had previously downloaded. The error code will show the Windows error indicating why VPOP3 could not open that file

If the error code is '32' it means that some other program was accessing the file when VPOP3 needed to access it. That other program might be a virus scanner, backup program, or, in rare cases, another running instance of VPOP3.