What are some alternatives?
When comparing MigrationWiz and IMAPSize, you can also consider the following products
imapsync - Console-based utility for migrating IMAP mailboxes.
Yippie Move - The world's best email transfer tool
MailStore - MailStore Home - A 100% free single-private-user desktop solution
OfflineIMAP - OfflineImap synchronizes email between an IMAP server and a MailDir or between two IMAP servers.
iSync - iSync is a software application published by Apple Inc.
audriga Email and Groupware migration - Easily migrate your email, contacts, calendar items and tasks to your new provider or server. No software installation is required.