Migrating an old mailbox

What gets migrated

The mail, and the way you had it sorted.

• Folders as they are — not everything dumped into one.
• Received and sent mail.
• The original message data, so sender, date and attachments stay exactly as they were.
• Trash and spam are skipped — moving them makes no sense.

How it runs

In the background, in batches, with visible progress.

1. In the portal, pick the mailbox to migrate into and the provider.
2. Enter the credentials for the old mailbox. For Gmail and Outlook that is an app password, not your ordinary one.
3. The job runs in batches; progress is visible and it can be stopped at any time.

The old mailbox is only read. Nothing there is deleted or changed, so if you change your mind it stays as it was.

The password is deleted as soon as the job ends — whether it finishes or fails.

The order that pays off

Migrate first, switch afterwards.

If you have your own domain, migrate the old mailboxes first and switch MX afterwards. The switch is the moment new mail starts arriving here; done earlier, you will be looking for it in two places.

Mail already on your computer

An Outlook or Thunderbird archive goes up by dragging it.

The migration above connects to your old server. When there is none left — the mail sits on your computer as an Outlook data file (.pst, .ost) or in Thunderbird's local folders — the direction reverses: you add our mailbox to the client you already have and drag the folders into it. The client uploads them.

What the client will ask for

• Incoming (IMAP): namailu.cz, port 993, encryption SSL/TLS.
• Outgoing (SMTP): namailu.cz, port 465, encryption SSL/TLS.
• Username: the full email address. Password: the password for that mailbox.

Outlook (Windows)

1. File → Add Account, enter your address here and choose manual setup with type IMAP; fill in the server and ports from the table above.
2. If the archive is a detached file, open it via File → Open & Export → Open Outlook Data File and pick the .pst. It appears in the left pane as another folder tree.
3. In the new mailbox, create the folder the archive should land in — say Archive 2019–2025.
4. Select the messages (Ctrl+A) or the whole folder and drag them into it. Outlook starts uploading.
5. For large folders move them in batches of a few thousand. Outlook uploads on a single thread and one huge block looks like a freeze.
6. When Send/Receive finishes at the bottom, check the message count in the folder before detaching the archive.

Thunderbird

1. Account Settings → Account Actions → Add Mail Account; after the address and password choose IMAP and check the server and ports against the table above.
2. The local archive lives under Local Folders. For an Outlook data file, open it in Outlook and drag from there — Thunderbird cannot open .pst on its own.
3. Create the target folder in the new mailbox (right-click → New Subfolder).
4. Select the messages and drag them in. Copying runs in the background and the status bar shows the progress.
5. To be safe, use right-click → Copy To instead of dragging — the originals stay where they are.
6. When it finishes, use right-click → Properties → Repair Folder so the index matches the server.

Where the limits are. The archive has to fit the mailbox size (1 GB by default, can be raised) and goes up message by message, so tens of thousands of messages take hours rather than minutes. The client sets the pace, not us — hence the smaller batches.

Create an account   Client setup in detail

Frequently asked

What people ask most.

What gets migrated?

Folders, received and sent mail, and the original message data. Trash and spam are skipped — moving them makes no sense.

Will I lose mail during the migration?

No. The old mailbox is only read; nothing there is deleted or changed.

How long does it take?

It depends on the size of the mailbox. It runs in batches in the background, so you need not watch it, and progress is visible in the portal.

Which providers do you support?

Gmail, Outlook, Seznam and any server that speaks IMAP.

What happens to the password for the old mailbox?

It is used only for the duration of the migration and deleted as soon as the job ends — whether it finishes or fails.

My mail is downloaded in Outlook — can I upload it?

Yes, but the other way round from a server migration: you add our mailbox to Outlook or Thunderbird and drag the folders into it. Uploading a .pst file on the web is not possible — the import always connects to an IMAP server.

How long does a large archive take?

It goes up message by message and your mail client sets the pace, so tens of thousands of messages take hours. Moving it in batches works better than the whole archive at once.

Create an account and migrate