Switching From eM Client to Another Email App

If you run eM Client on Windows, some of what looks like 'your Gmail' or 'your work inbox' may actually only exist on your PC. eM Client keeps a local database of everything it manages — including full mailboxes for POP3 and Exchange accounts — inside your Windows user profile. So working out how to switch from eM Client to another email client is really two separate jobs: reconnecting the mail that already lives on a server, and rescuing whatever only ever lived in that local database.

Uninstall the app without checking which accounts are local-only, and mail you assumed was safely 'in the cloud' can disappear with it. This guide covers what moves on its own, what you carry over by hand, and how to run both clients side by side while you check the switch worked — whatever desktop or web-based client you're moving to.

It's also written for ex-Postbox users. Mozilla's Postbox was acquired in October 2024, and eM Client published an auto-detect migration path that moved many Postbox installs over without anyone deciding, deliberately, that eM Client was the client they wanted. If that's you, everything below still applies — you're just switching a second time.

What Actually Moves and What Doesn't#

The single fact that decides how hard your migration is: which protocol each account uses. eM Client treats a synced IMAP or Exchange account very differently from a POP3 account or a folder you built by hand inside the app.

eM Client's own database lives at AppData\Roaming\eM Client in your Windows user profile (Menu → Settings → General → Storage shows and lets you move the exact path). Anything that only exists in that folder does not exist anywhere else, and moving to a new client doesn't automatically carry it along.

• IMAP accounts (Gmail, Outlook.com, iCloud, Fastmail, most modern providers) — mail lives on the mail server. eM Client is a window into it, so adding the same account in a new client re-downloads everything on its own.
• Exchange/EWS accounts — mail, calendar and contacts usually live on the Exchange server too, so reconnecting recovers most of it. Shared-mailbox access and delegate permissions are granted per client, though, so those need setting up again.
• POP3 accounts — by default, POP3 downloads mail and may remove it from the server after a set number of days. Anything already pulled into eM Client is local-only unless 'leave a copy on server' was turned on for that account.
• Local folders, search folders and anything under 'Local Folders' — always local-only, no matter which account type they're attached to.
• Contacts and calendar events you typed directly into eM Client, rather than syncing from a CardDAV/CalDAV or Exchange source — local-only.
• Rules, signatures, templates, snooze/watch settings and tracking-pixel blocking — these are eM Client configuration, not mail. No client imports another client's settings; you rebuild them.

Pre-Migration Checklist#

Do this before you touch any account settings. It takes under an hour for most single-user setups and it's the difference between a clean switch and a support ticket to yourself.

• Open Menu → Accounts and list every account with its protocol (IMAP / POP3 / Exchange). This single list tells you which accounts need nothing and which need an export.
• For each POP3 account, check whether 'leave a copy on server' is on. If it's off, decide now whether the server copy or eM Client's local copy is the one you trust — see the callout below before you add that account anywhere else.
• Run Menu → Backup to create a full eM Client database backup before changing anything. This is your undo button for the whole migration.
• Export contacts to a .vcf file and calendar to a .ics file as a second, portable copy, separate from the eM Client backup format.
• Note your licence type — subscription or one-time purchase — and where you'd manage or cancel it if you decide to stop paying.
• Gather sign-in details for every account, including any app-specific password set up for two-factor authentication years ago and since forgotten.

Steps to Switch From eM Client#

1. 1

   Inventory and back up first

   Complete the checklist above: list every account by protocol, back up eM Client's database (Menu → Backup), and export contacts/calendar to .vcf and .ics.

2. 2

   Export anything local-only

   For POP3 mail and any local folder, select the folder and use Menu → Export to save it as .eml files (eM Client's supported export format). Most current desktop and web clients can import .eml, either directly or via a drag-and-drop.

3. 3

   Install and open the new client

   Don't touch eM Client yet. Get the new app installed and signed in to your primary account first, so you can compare inboxes side by side.

4. 4

   Reconnect server-synced accounts

   Add each IMAP and Exchange account to the new client using the credentials or app passwords you gathered. These re-download in the background — this is the part of the switch that needs no manual export.

5. 5

   Import the local-only mail, contacts and calendar

   Import the .eml files into a matching folder structure, then import the .vcf and .ics files. Check folder names and any nested structure — imports don't always preserve nesting exactly.

6. 6

   Rebuild rules, signatures and filters

   Recreate mail rules, signatures, reply templates and any spam or tracking-pixel rules in the new client. None of this transfers automatically between any two mail clients, not just eM Client.

7. 7

   Verify a full send/receive cycle on every account

   Send a test email from and to each connected address, and confirm calendar invites still create events correctly. Do this before the next step, not after.

8. 8

   Decide on the eM Client licence, then uninstall

   Cancel a subscription in eM Client's account portal if you're not keeping it as a backup reader; a one-time purchase simply goes unused. Keep the app installed until you're confident, then uninstall.

What Breaks When You Leave eM Client#

Most reported migration problems trace back to one of the rows below — specifically, mail or settings that the switcher assumed were server-side and turned out to be local.

The pattern across that table is the same idea twice: anything eM Client only stored, rather than synced, needs an explicit export step. Nothing in the new client can pull data out of eM Client's database on its own — it has to be handed over as a file.

Rollback Plan#

Keep eM Client installed, licensed and untouched until the new client has completed at least one full send/receive cycle on every account and you've confirmed contacts and calendar entries look right. That's the entire rollback plan: don't remove your safety net before you know you don't need it.

If something looks wrong in the new client — a folder is missing, a calendar entry didn't come across — reopen eM Client and re-export rather than guessing. The Menu → Backup file you made during the checklist restores the exact state you started from if the export step itself went wrong.

Doing It Without Downtime#

You don't need an outage window. IMAP and Exchange both support more than one client reading the same mailbox at once, so the server-synced part of the switch can run with both apps open and receiving mail in parallel.

POP3 is the one protocol where two clients at once causes a problem, since a POP3 client can be set to delete mail from the server after pulling it. That's why the checklist above asks you to check 'leave a copy on server' first — with it on, both apps read the same mailbox without either one deleting anything.

• Add accounts one at a time, verifying each before moving to the next, rather than migrating everything in one pass.
• Leave eM Client's notifications on during the overlap so you'd notice if mail stopped arriving somewhere.
• Do the export-heavy accounts (POP3, local folders) first, while you still have patience for double-checking file counts.

Where AI Emaily Fits#

The reason this migration takes real effort is that eM Client's local database is the source of truth for anything not synced to a server. AI Emaily doesn't hold that role for your mail: it connects to your existing Gmail, Outlook or IMAP accounts directly and works from what's on the server, with drafts approved before they send and an audit trail with undo. If you switch away from AI Emaily later, that's a server-side reconnection like the IMAP rows above, not a local-archive rescue like this one.

AI Emaily runs as a web app and as a downloadable Windows installer, on a 7-day free trial on the plan that includes the agent (card required, $0 if you cancel before day 7 — there's no permanent free tier). We build AI Emaily.