Mail Authentication issue

[ChrisO@]

Hi

Every now and then clients phone in and says the outlook is asking them for a username and password. They can ping and telnet to the mailserver but it keeps asking for logon credentials. If I restart the mailserver ,via plesk service monitor, it works again. What can this be?

Any Help would be appreciated.

 

[tivuron]

I am having the very same issue but just with one email account in one domain????

I've deleted the account twice and recreated it. The client logs on and receives mail for a few hours and then it goes back to failing in the log on, both in outlook and in webmail.

If anyone has a clue, please advise.

thanks.