Test the connection to your mailbox
Entirely free, whatever the size of your mailbox — no account, no subscription.
How it works
- Enter your mailbox credentials — address, password (or app password) and the IMAP server settings (server, port, SSL).
- Run the test — MailSync connects to your mailbox read-only, without changing anything.
- Get the result in seconds — connection success or failure (with the reason), the estimated size of your mailbox, and the list of your folders with the number of messages in each.
Use cases
- Checking your credentials before a transfer or backup — make sure the connection works before starting a longer operation.
- Diagnosing a connection failure — understand why an email client or another tool can't connect to your mailbox.
- Discovering the real size of your mailbox and folders — before a clean-up or deciding on an archiving plan, without having to open each folder one by one.
- Validating an app password — after generating one on Gmail or Outlook, confirm it works before using it elsewhere.
What this tool doesn't do
- The test only works over IMAP: mailboxes only reachable via POP3, or through a closed proprietary Exchange connector, can't be tested with this tool.
- The connection is read-only: MailSync never modifies your mailbox, never deletes anything, never moves anything.
- MailSync doesn't read the content of your messages: it's limited to connection, size and folder metadata, without ever opening an email.
- The tool doesn't fix settings for you: you need to know your mailbox's connection settings (IMAP server, port, SSL), even though MailSync auto-detects settings for the most common providers.
Frequently asked questions
What does the tester actually check? +
The tester connects to your mailbox with the IMAP credentials you provide, read-only. It tells you whether the connection succeeds or fails, the estimated size of your mailbox, and the list of your folders with the number of messages in each.
Do I need an app password (Gmail, Outlook…)? +
It depends on your provider. If you've enabled two-step verification on Gmail or Outlook/Microsoft 365, you'll need to generate a dedicated app password in your account's security settings, and use it here instead of your usual password.
What IMAP settings do I need to know (server, port, SSL)? +
You need the incoming IMAP server address (for example imap.gmail.com), the port (often 993 for SSL) and whether the connection should use SSL/TLS. This information comes from your host or email provider; MailSync auto-detects the settings for the most common providers.
Does the test change my mailbox? +
No. The connection is read-only: no message is deleted, moved, or marked as read. MailSync only reads the list of folders and the number of messages they contain.
Why is my connection failing? +
The most common causes are: an incorrect password, IMAP access disabled in your mailbox settings, an app password required (two-step verification enabled) that hasn't been generated, or the wrong server/port. The error message shown after the test points you to the most likely cause.
Are my credentials stored after the test? +
No. Your IMAP credentials are encrypted for the whole duration of the test, then erased as soon as it finishes. If you're signed in to your MailSync account and chose to save the mailbox, only that one is kept (encrypted) so you don't have to retype credentials next time; you can delete it at any time.