Hi,<br><br>I have a Mailserver setup with Qmail+Vpopmail+courier-imap with 2000 users.The authentication in vpopmail was in plaint text file based.Right now the issue<br>is while opening a user email box with 50-100 mails it is opening 
fastly.But for email-boxes with attachments and increased number of mails it take long time<br>to open the Imap connection.<br>So I would like to change the Imaps to Dovecot.Please suggest if I can migrate from courier-imap to dovecot with vpopmail and qmail without changing the present username and passwords.
<br><br>Thanks in advance for any help.<br><br>Regards<br>John<br>