Transferring from Plesk to cPanel - Duplicate POP E-mails


Active Member
Nov 21, 2017
cPanel Access Level
Root Administrator

Sorry to bother you but I was hoping someone might be able to help with this one.

We have two servers, a Plesk system and a cPanel one.

We are migrating customers from the Plesk server to cPanel.

We have just transferred over a couple of customers but have found an issue. The customers had POP e-mail accounts set up and therefore when they tried to connect over the weekend, their devices connected to the new server and downloaded a duplicate copy of the e-mails.

Is there a way to stop this? I'm guessing not as their devices are seeing the new server and assuming that the e-mails have not been dowloaded already but I'm asking just-in-case there is something that I've missed.

Kind regards



Staff member
Apr 11, 2011
Hi James,

It looks like we sent a response to this inquiry via a support ticket. Here's a copy of the response for others that may find this thread:

Unfortunately no, there is no way to prevent that. This is a common issue with using POP3 instead of IMAP.

It can occur with IMAP as well but not as frequently as with POP3. Indeed it does have to do with how an email client downloads email.

The biggest pitfall of POP3 is the implementation among email clients. For example, in Microsoft Outlook typically it is configured to leave a copy on the server for a certain amount of time. This is what causes the duplicate email trouble. Outlook downloads the email and stores information about that email on your computer so that when it goes to download email again it can try to skip that one and prevent a duplicate download.

POP3 is rapidly becoming an artifact of the past. With many now accessing their email over mobile devices they are turning to IMAP to handle their email.

Clients using POP3 get confused about which messages have already been seen, which would then download another copy of a message that it has already downloaded, creating a duplicate copy.

This problem is magnified when you try to modify certain settings with your email provider or if you migrate the email to a different server. When the copies left on the server that Outlook has already downloaded are migrated to another server, Microsoft Outlook says "hey look, this message looks new" and downloads all the email copies again from the new server. This becomes a problem because it has already downloaded the emails once and it is just confused so it downloads them all again from the new server.

So unfortunately there is little that can be done about that and is the reason why IMAP should be used instead of POP3.
Let us know if we can be of any further assistance.

Thank you.