Email migration without losing a thing
Changing email providers sounds simple until you realise years of messages, folders, and read states all have to arrive intact on the other side. This is where migrations quietly lose things. Here is how to move email safely, and the open source tool we built to do it.
Good email migration services move every message, folder, and flag from the old provider to the new one without losing or duplicating anything, and without surprising your people mid workday. The safe way is an IMAP level copy that preserves folder structure and read states, run in a verifiable pass with the old mailbox left untouched until the new one is confirmed complete. We built MailMigrator, a self hosted IMAP email mover, so this can be done carefully and with your data staying in your hands.
Where email migrations lose things
Email feels like it just moves, but a mailbox is more than a pile of messages. It has a folder structure people rely on, flags for what has been read and replied to, important messages people have starred, and years of searchable history that is often a business record. A careless migration treats email as a simple copy and quietly drops some of that: folders collapse, read states reset, a date range goes missing, or messages arrive twice.
The damage usually shows up after the switch, when someone goes looking for an old thread and it is not there, or opens their inbox to find hundreds of old messages marked unread. By then the old provider may already be gone. The whole point of taking migration seriously is to avoid that moment, because the cost of losing years of correspondence is far higher than the cost of moving it carefully in the first place.
The safe way to move
The reliable approach is a migration that works at the IMAP level, the protocol mail clients use, copying each message along with its folder and its flags so the new mailbox mirrors the old one faithfully. It should be idempotent, meaning you can run it more than once without creating duplicates, which matters because real migrations rarely finish perfectly on the first pass and need to be resumed or topped up.
Crucially, the old mailbox should be left untouched until the new one is verified complete. You copy, you check counts and spot check folders, and only then do you cut people over and eventually retire the old account. That read only treatment of the source is what makes the whole thing safe to retry, because the worst case is simply running it again rather than discovering the original is damaged. Careful beats fast every time with something this hard to undo.
The tool we built for it
MailMigrator is a self hosted IMAP email mover we built and released as open source for exactly this job. It connects to the old and new mailboxes over IMAP and copies messages across while preserving the folder structure and flags, so the destination looks like the source rather than a flattened dump. Being self hosted means it runs in your own environment and the mail passes through your hands, not a third party service you have to trust with years of private correspondence.
We are deliberately modest about what it is. It is a focused tool that does mailbox to mailbox IMAP migration carefully, not a sprawling platform. For many moves that is exactly the right scope, because the job is narrow and the priority is doing it safely and verifiably rather than adding features. It is there for teams who want to run their own migration, and it is the same tool we reach for when we run one for a client.
Planning the cutover
The copy is only part of the job. The other part is the cutover, the moment incoming mail starts flowing to the new provider instead of the old, which is governed by your DNS records and takes time to propagate across the internet. Plan for a window where mail could arrive at either place, keep both mailboxes live through it, and do a final top up copy once the switch has fully settled so nothing that landed late is left behind.
Timing and communication matter as much as the technical steps. Move during a quiet period, tell people what to expect and when, and have a clear way to check that nothing went missing before you retire the old account. A migration that is technically perfect but sprung on people mid workday still feels like a failure. Done with a little planning, the move can be almost invisible to the people who depend on their email every day.
Common questions
Will I lose my folders and read and unread status?
Not with a migration done properly. An IMAP level copy preserves the folder structure and the flags, so the new mailbox mirrors the old one. Losing those is a symptom of a careless move, which is exactly what careful tooling avoids.
Can I move email between any two providers?
In general, yes, as long as both support IMAP, which nearly all mainstream providers do. The approach copies mailbox to mailbox over that protocol, so it is not tied to one vendor's import feature.
Is MailMigrator free to use?
Yes, it is open source and self hosted, so you can run it in your own environment. That also means your mail stays in your hands rather than passing through someone else's service during the move.
Can you just run the migration for us?
Yes. We can plan the cutover, run the copy with verification, and handle the DNS switch so the move is as close to invisible as possible, or set you up to run it yourself with the same tool.
Moving email and worried about losing history?
Tell us where you are moving from and to, and we will plan a migration that arrives complete, verified, and quiet, using tooling that keeps your mail in your hands.