New into maildir format (having a issue)

[bsasninja]

I had a customer with 100 emails in a server with mbox format. I converted it to maildir format.
He has activated keep copy of mails in the server in his outlook.

As I read maildir detects existing emails as new and the mail client downloaded the 100 mails again.

And this happened to him 4 times, the 100 emails have been downloaded 4 times, so I have to move his emails to the draft folder of the webmail to avoid downloading all time.

This issue happens only with mails that were using the mailbox format and then converted to maildir??? This will not happen again with new emails delivered to the mailbox??

Mails that were in mbox format says something like this 11029323.1293.mbox:2 and mails in maildir format says something like 10100133.23882.server.myhostname.com

Thanks

[Spiral]

He just simply needs to download the mail through to completion ONCE after the conversion ...

After that, it won't send him the same duplicate mail again.

I think the problem here is the client may be seeing the duplicate messages
coming in and hitting cancel before the transfer is complete. That effectively
tells the email program to start over at the beginning again next time
the client checks his mail.

[chirpy]

Additionally, if he insists on leaving email on the server he should be using IMAP to access it and not POP3. POP3 was never designed for email to be left on the server - that's a client side feature only and, as Spiral as said, problems with it are indicative of an isse at the client end.

[Spiral]

Just some clarification from what Chirpy and I just said in simpler terms ....

There is basically two standard methods of retrieving mail and most
email client programs out there can be configured to operate in
either of these two modes:

POP3 - Email is moved from the email server to the client's computer
when checking mail and afterwards the mail is stored inside
the email program itself such as Microsoft Outlook, Thunderbird, etc.

IMAP - Email is stored out on the email server and is remotely managed
and viewed. With IMAP, the email program such as Thunderbird
and others just acts as a login portal into your email account and
the email physically stays out on the mail server.