After a Mail Migration, Check Whether New Mail Still Reaches the Old Account

Know what the migration did—and did not do

First, identify whether your migration copied existing messages, arranged continued delivery, or did both. These are different outcomes. A one-time copy can transfer mail that was present at the time of migration, but it does not by itself establish that later messages will be delivered to the new account.

Check the instructions or status information for the migration method you used. If you cannot tell whether ongoing delivery is set up, do not assume it is. Continue monitoring the source inbox and ask the relevant mail administrator or provider what delivery arrangements apply. For a work domain, make changes only if you are authorised to administer it.

Make a two-inbox check part of the transition

For a period that suits your work and the expected use of the old address, check the source and destination accounts regularly. There is no universal monitoring period: it depends on how widely the old address is used and whether senders have been told about the change.

Look beyond the inbox. Check folders where incoming mail might be sorted, such as spam or archived mail, and search each account for messages from the changeover period. Use the same sender, subject, or date range in both accounts where possible. A message missing from the destination is a reason to investigate, not proof on its own that it was lost.

• Open both accounts and note the latest relevant message in each.
• Search for expected messages using the sender or subject, not just the inbox view.
• Record any message found only in the source account so you can follow it up.

Handle messages that arrived late

When a useful message appears only in the old account, decide whether it needs action before moving or forwarding it. A copy in the destination can help keep your records together, but preserve the original if its attachments, conversation context, or delivery details matter. For an important request, reply to the sender from the address you want them to use going forward and clearly identify that address.

Do not assume a forwarding rule, import, or sync is active simply because earlier mail appears in the new account. If you use a forwarding or delivery setting, verify it with a message sent from an account you control, then inspect both inboxes and relevant folders. Avoid sending sensitive information in a test message.

Use a small, controlled check

A test can confirm that a particular route worked at that moment; it cannot prove that every sender or future message will follow the same route. Use an address you control, send a distinct subject, and check the source and destination separately. If the message appears in only one place, note where it arrived and review the migration or delivery setup before relying on it.

From: [your test account]
To: [old-address@example.com]
Subject: [Migration check — date]

Then send a separate message to [new-address@example.com]. Check both accounts for each subject and note where each message appears.

Keep account access and dependencies in view

Before closing or cancelling the old account, consider what still depends on it: recovery addresses, account sign-ins, subscriptions, shared files, or contacts who have not updated your details. Change those settings while you can still access the source account, and verify important changes through the relevant service.

For a business mailbox, coordinate with the authorised workspace or domain administrator. Domain and mailbox controls depend on role, plan, and provisioning, so an individual user may not be able to change delivery settings. Do not make domain changes unless you have the required authority.

Close only after you can explain the remaining risk

You are in a better position to retire the old account when you have checked both accounts across the changeover, handled messages that arrived only at the source, updated important contacts and dependencies, and confirmed the intended delivery setup. Keep a note of the date you last checked and any unresolved senders or services.

If new mail continues to reach the old account, keep it available and investigate rather than assuming the migration failed or that closure will redirect messages. If nothing has arrived recently, that is useful evidence but not a guarantee that nobody will use the address later. Decide based on your account requirements and the consequences of missing future mail.