Switch from Courier to Dovecot

[TSJaysonG]

How long on average does it take to convert a Courier server to Dovecot? Lets say there are 400 users and ~1000 email accounts. Does it take longer if there are more accounts?

[garrettp]

When converting between the two you're not actually changing the mail storage format (unless you were previously still using mbox), however a note inside the WHM leads me to believe there is a bit of extra overhead during this conversion the more users you have:

When checked, the settings files for each mailbox will be converted into the format for the new mail server. This includes information about read messages, mailbox subscriptions, etc. Unchecking this box will cause your clients to lose their mailbox settings but will speed up the migration.