Same mail is downloaded multiple times in outlook

It happens many times that certain number of mails are being downloaded in MS Outlook multiple times from the server as a never ending process.

I can't find a solution on this. Need Help.

Thanks.

 

In MS outlook I don't know of any setting like fetchmail /getmail.
Where I should look for these settings.

Yes the account is configured as POP3 in MS outlook.

 

There is no account configured under Fetchmail in ISPCONFIG. (Fetch emails from external POP3 / IMAP servers).

Yes in outlook keep copies of email on server for 10days is selected. But the mails are being downloaded multiple times in the same place.

 

I want to add if it helps
That this behavior of downloading multiple times is not regular. It happens randomly.

 

Till, did you find any problem with the above settings?

 

Ok, is it related to system time of the server.

Does the mails already downloaded are marked as already downloaded based on time and how I can overcome this problem?

There must be some solution for this as the client is complaining about this quite so often.

 

Thank you so much Till.

Now what I understand is that the issue of multiple download may be

1.an issue of system time on the server or
2. There is some setting or some bug in outlook which is making outlook to download multiple times.

Now to rule out & be sure that the issue is related or not related to system time on the server where I should look for. Is there any log file created for system time synchronizing with the NTP server.