How to Import Email History Into a New or Shared Inbox

To import email history, bring the old messages into the mailbox your team will actually work from, then check the results. In Gmail, that means the built-in import from another account (POP-based, mail only). In Microsoft 365, it means an IMAP migration for mailboxes still live somewhere else, or a PST import for archived files. A shared support inbox that connects to that mailbox can then work with the history you moved in.

This guide covers the methods, the limits that trip people up, what happens to dates, folders and attachments, and how to confirm nothing went missing.

TL;DR

• Import into the mailbox first, then layer the shared inbox on top. History lives in Gmail or Microsoft 365, not in the team tool.
• Gmail’s import brings in messages but not the source account’s folders or labels, so plan your own labeling afterward.
• Microsoft 365 offers IMAP migration for live mailboxes and PST import through Purview for archives.
• Watch the limits: 500,000 items per mailbox and 35 MB per message on Microsoft’s IMAP route.
• Verify with message counts, date spot checks and a few attachment tests before you retire the old account.

Table of Contents

• Decide where the history should live
• Import old email into Gmail or Google Workspace
• Import old email into Microsoft 365
• What survives the move, and what doesn’t
• Step-by-step: a safe import for a support team
• How to verify the import
• Perspective: connect first, then collaborate
• Ready to work from one shared inbox
• Common problems and how to handle them
• FAQ
• Sources

Decide where the history should live

Before you pick a tool, answer one question: which mailbox will your team work from?

For most small support teams the answer is one of two places. Either a Google Workspace or Gmail mailbox such as support@yourcompany.com, or a Microsoft 365 mailbox or shared mailbox. Your history needs to end up there. If you’re moving off a help desk, a group alias or a personal address, the old messages are the part that is easy to forget until a customer writes back about something from last spring.

Three situations cover almost every case:

1. Old messages sit in another live email account. Think of a founder’s personal Gmail, an old domain mailbox, or a departing employee’s inbox. This is a mailbox-to-mailbox import.
2. Old messages sit in files. You have PST exports from Outlook, or archives from a previous provider. This is a file import.
3. Old messages sit inside a help desk or group tool. The history is in ticket records or group archives. This needs an export from that tool first. Our guides on moving from a help desk to a Gmail or Microsoft 365 shared inbox and migrating Google Groups while keeping history walk through those two paths.

The rest of this article handles the first two, since they are what most people mean when they search for this.

Import old email into Gmail or Google Workspace

Google’s own help page says you can use Gmail to import old and new messages from another email account. The same page is clear about the catch: the source account’s folders and labels do not come along.

The import is configured from Gmail’s settings on a computer, under Accounts and Import. A few requirements from Google’s documentation:

• The source account must support POP, since that is how Gmail pulls the messages.
• You set it up inside the destination Gmail account, not the old one.
• Google says that after the import, messages sent to the old address are forwarded for 30 days, and the new Gmail address is displayed for 60 days or until you delete the reminder.
• Administrators can disable the import option for work or school accounts. If the option is missing from your settings, ask your Workspace admin before assuming something is broken.

That 30-day forwarding window matters for support teams. If you are retiring an old address that customers still write to, treat those 30 days as a grace period, not a plan. Update your website, invoices and email signatures while forwarding is active.

What happens to folders and labels

Since labels do not carry over in the personal-account import, you have two options. You can recreate a small set of labels in the destination and apply them to searches (for example, by sender or subject). Or you can accept a flat archive and rely on search.

For a larger, admin-led move into Google Workspace, the picture is different. Google’s migration documentation states that folders are migrated as distinct labels in Gmail, usually with the same name as the source folder. It also notes that folders with paths longer than 225 characters are not migrated, and the messages inside them are skipped too. If your old system had deeply nested folders, flatten them before you start.

One more detail from Google’s migration guidance: if users end up with more than 500 labels, Gmail can take longer to load. A tidy label structure is a performance matter, not only a cosmetic one.

Import old email into Microsoft 365

Microsoft gives you more than one route, and the right one depends on whether the old mail is live or in files.

IMAP migration for mailboxes that are still live

Microsoft documents an IMAP migration that moves items from a user’s inbox or other mail folders. It does not move contacts, calendar items or tasks. Key points from that page:

• You need access to the source mailboxes.
• Microsoft recommends disabling MRM and archival policies before you start.
• The limits are 500,000 items per mailbox and 35 MB per email.

Those limits are where large histories get stuck. A support inbox with ten years of attachments can hit 35 MB on individual messages without anyone noticing. Decide in advance what to do with oversized messages: ask the sender to resend, or keep the old mailbox read-only as an archive.

PST import for archived files

If you hold PST files, Microsoft states that U.S. organizations can bulk-import them through the Microsoft Purview Import service, using either network upload to temporary Azure Storage or BitLocker-encrypted drive shipping.

The process separates four jobs: transferring the files, mapping each file to a mailbox, optionally filtering, and running the import. The mapping step is the one people underestimate. Microsoft requires an import-mapping CSV that assigns each PST to a target user mailbox or archive mailbox. An administrator then creates the import job in the Purview portal and can apply filters after analysis.

For a single person’s file, you can skip the bulk service. Microsoft Support lists importing email, contacts and calendar from a PST file in Outlook for Microsoft 365, Outlook 2024, 2021, 2019 and 2016. That works well for one founder’s archive, less well for a team of fifteen.

Importing into a shared mailbox

A Microsoft 365 shared mailbox has no login of its own, so you generally cannot import into it the way you would a personal mailbox. Plan the import in terms of the mailbox that will be reachable and who has access. If you are still deciding how to structure it, our explainer on what a Microsoft 365 shared mailbox is covers the basics, and permissions for shared inboxes explains Full Access and Send As.

What survives the move, and what doesn’t

Support teams care about four things in an old thread: when it was sent, who sent it, what was attached and how it was organized. Here is what the documentation says about each.

The duplicate check is useful if a run is interrupted and you start it again. It is not a reason to run the same import five times without looking at the results.

Step-by-step: a safe import for a support team

This sequence works for most small teams, whichever route you use.

1. Inventory the sources. List every mailbox, PST file and group that holds customer history. Note roughly how many messages each has and the oldest date you care about.
2. Set a cutoff. You rarely need everything. Many teams keep the last two to three years of customer conversations and archive the rest in a read-only form. A shorter window means a faster import and fewer limit problems.
3. Clean before you move. Flatten deep folder trees, remove obvious junk and check for very large messages. This avoids the 225-character path issue and the 35 MB per message limit.
4. Check permissions. Confirm you can reach the source mailbox and that your admin has not disabled import in the destination. Microsoft’s IMAP route also needs source access.
5. Run a pilot. Import one small mailbox, or one year of mail, first. Open a dozen threads and compare them with the originals.
6. Run the full import. Do it outside peak hours so your team is not working in a half-loaded inbox.
7. Verify (see below), then switch customers over to the new address.
8. Keep the old source for a while. Do not delete the old account until your checks pass and your forwarding window has closed.

How to verify the import

A completed job does not mean a complete import. Check these before you sign off:

• Counts. Compare the number of messages in the old and new mailboxes, folder by folder or label by label. Small gaps are worth explaining, not ignoring.
• Dates. Sort by date and look for a cluster of messages all stamped with the migration day. That is the signature of non-standard date headers.
• Attachments. Open a handful of older messages with PDFs, images and spreadsheets. For anything over 25 MB in a Google migration, confirm the Drive link opens for the people who need it.
• Threads. Search for three or four real customer names and make sure the full conversations appear in order.
• Skipped items. If a folder name was very long or a message was very large, expect it in your gap list.

For failed or missing messages, the fix is usually to correct the cause (shorten a folder path, shrink or separate an oversized message, fix permissions) and rerun the affected slice. Because of the duplicate check described in Google’s documentation, rerunning a slice should not stack up copies of what already arrived.

Perspective: connect first, then collaborate

We see the same mistake often. A team decides it needs a new help desk, then spends weeks worrying about how to pour years of email into it. The history was never the hard part. The hard part was choosing a tool that wanted to own it.

Our view is simpler: your email already lives in Gmail or Microsoft 365, so keep it there. Get the old messages into the mailbox using the methods above, which are documented by Google and Microsoft themselves, and let the shared inbox sit on top as the place where your team assigns, replies and adds internal notes.

That is why SendSync is built to connect to your existing mailboxes with no DNS changes, rather than asking you to move into a separate system. You do the import once, in tools your admin already knows, and your team keeps working in the mailbox it trusts. With unlimited users and flat pricing, adding the person who helps during a busy month does not change your bill.

Nick

Ready to work from one shared inbox

Once your history is in the right mailbox, the next step is giving your team a clean way to work in it. SendSync connects your Gmail or Microsoft 365 mailbox, with unlimited users and no per-seat fees. Plans are published as Founder at $10 per month, Starter at $30 per month, Growth at $80 per month and Scale at $200 per month, and every plan starts with a 14-day free trial.

You can see the plans and start a trial with the mailbox you just imported into. If you use Google Workspace, our guide to connecting a Gmail team inbox in minutes is the natural next read. Microsoft 365 teams can follow the Microsoft 365 team inbox setup guide.

Common problems and how to handle them

“The import option isn’t in my Gmail settings.” On work or school accounts, administrators can turn it off. Ask your admin to enable it or to run the import at the organization level.

“My labels disappeared.” In the personal-account import, labels from the source are not imported. Rebuild a short set of labels and use searches to apply them in bulk.

“Everything shows today’s date.” This points to date headers that do not follow RFC 2822. The messages themselves are still there; the original date may be recoverable from the message body or from the source account, so keep the source until you’ve decided what matters.

“The job stalls on one mailbox.” Check the item count and message size against Microsoft’s 500,000-item and 35 MB limits. Splitting the mailbox by year is a practical way around the item cap.

“Our team shares one address and has no history tool.” If a shared address was set up as a forwarding alias, the history sits in several people’s inboxes. Collect it from each one, import into the single destination mailbox, and remove the forwarding rule only after that. Our piece on setting up a shared inbox without forwarding explains why.

FAQ

Can I import my email history into Gmail without losing labels?

Not with the personal-account import. Google says it imports messages but not the source account’s folders or labels. For admin-led migrations into Google Workspace, folders are migrated as labels with usually the same name. Either way, plan to review your labels afterward.

How much email can I import into Microsoft 365?

On Microsoft’s IMAP migration, the documented limits are 500,000 items per mailbox and 35 MB per email. If your mailbox is larger, split it by year or keep part of it as a read-only archive.

Does importing email also move contacts and calendars?

It depends on the route. Microsoft’s IMAP migration does not move contacts, calendar items or tasks. Outlook’s PST import can bring in email, contacts and calendar from a PST file, so use that for a fuller move of one person’s data.

How long should I keep the old mailbox after the import?

Keep it until your verification checks pass and your forwarding window has ended. In Gmail’s import, forwarding from the old address runs for 30 days, so many teams hold the source at least that long.

Do I need to import everything?

No. Most support teams get what they need from a recent window of customer conversations. A cutoff keeps the import quick and reduces the chance of hitting size or item limits.

Sources

• Check emails from other accounts, Gmail Help
• Check emails from other accounts (settings and forwarding details), Gmail Help
• What is migrated?, Google Workspace Admin Help
• Monitoring points for Exchange, Google Workspace Migrate
• What you need to know about migrating your IMAP mailboxes, Microsoft Learn
• Learn about importing organization PST files, Microsoft Learn
• Import and export Outlook email, contacts, and calendar, Microsoft Support

Recommended

• Connect a Gmail Team Inbox in Minutes: 2026 Guide
• Support Managers, Move From a Help Desk to a Gmail or Microsoft 365 Shared Inbox
• Microsoft 365 Team Inbox Setup: 2026 Guide
• Shared Inbox Workflows: A Practical Guide for Small Teams