imap-migrate vs Stellar Migrator for Exchange

imap-migrate is a free, open-source command-line tool for transferring the contents of one email folder between IMAP hosts. It can work with providers that support IMAP, including Gmail, Outlook, Fastmail, Yahoo and custom servers. The tool preserves original received dates and flags such as Seen and Flagged, and shows progress, transfer speed, success and error counts, plus estimated time remaining. It records actions in migration.log. Its README says interrupted migrations can be rerun without duplicating emails; the --dry-run option checks connection and settings without moving messages. Credentials can be supplied as command-line arguments or environment variables, with environment variables recommended by the README as the more secure option. Both accounts need IMAP access enabled, and the tool requires Python 3.12 or higher; uv is recommended for dependency management. It runs on Linux, macOS and Windows and is licensed under MIT. It does not rebuild a full folder structure or migrate provider-specific features such as Gmail labels or categories. Bug reports and contributions are invited through GitHub issues and pull requests.

Stellar Migrator for Exchange moves mailboxes among Exchange Server and Microsoft 365 environments, including transfers between Microsoft 365 tenants. It supports primary, shared, and archive mailboxes as well as public folders, and can run cutover, staged, or hybrid migrations all at once or in batches. Delta migration transfers new or changed data after an initial move. Up to 10 mailboxes and their items can be migrated simultaneously. Users can match mailboxes automatically or map them manually, including with a CSV file, select folders such as email, contacts, calendars, tasks, notes, and journals, and filter mail by date range. Failed or incomplete migrations can be rerun, with automatic retries set from 1 to 5 attempts. It runs on Windows and requires at least 8 GB of memory. The free trial covers 2 mailboxes and includes all migration capabilities; Mailbox Pricing is $250, paid once, billed $10 Per Mailbox, with quantity selected on the page and one license per source mailbox.