Migrate IONOS Email to Google Workspace (2026 Guide)

IONOS (formerly 1&1) is a frequent migration source in Europe and increasingly in the US. The email stack is solid — Dovecot-based IMAP, predictable folder semantics, decent uptime — but it's not built for high-throughput migrations. IONOS throttles aggressively, the webmail-based contacts and calendars don't come along for the ride, and the control panel hides a few admin features behind menus that aren't obvious until you've dug for them. This guide covers what changes when you move IONOS email to Google Workspace, with the specific gotchas IONOS introduces.

What you have on IONOS#

IONOS sells email under several product names — Mail Basic, Mail Business, and Mail Premium are the current lineup, but you may also see older labels like "1&1 Mail" depending on when the account was set up. The capabilities differ slightly, but the migration mechanics are the same.

Migrates over IMAP: INBOX, Sent, Drafts, Trash, Spam, and any user-created folders. Messages, attachments, internal date, flags. Folder names with non-ASCII characters (common for German and French users — "Gesendet", "Brouillons") encode in modified-UTF-7 over the wire.

Doesn't migrate over IMAP: Contacts (CardDAV), calendars (CalDAV), tasks, notes, server-side filters configured in the IONOS webmail, vacation autoresponders, forwarders, aliases, and any shared folder permissions. Each of these needs a separate plan.

Prep Google Workspace#

Get the destination ready.

Sign up and verify#

Create the Google Workspace tenant at workspace.google.com. Verify the domain via TXT (Google publishes a unique value per tenant). Do not change MX yet.

For sizing, Business Starter (30 GB per user) covers most IONOS migrations because IONOS mailboxes tend to be small. If anyone's mailbox is over 25 GB, Business Standard (2 TB) gives you headroom.

Create users matching IONOS exactly#

Bulk import users via CSV. Match the primary SMTP address to the IONOS address — info@example.com → info@example.com. Don't change capitalization, dashes, or dots; some message threading and folder-mapping logic is case-sensitive.

For IONOS aliases (added in the IONOS control panel under Email → Email Addresses → Aliases), recreate them as alternate email addresses on the matching Google user. If a single IONOS mailbox receives mail for multiple aliases, all of those aliases must be added to the Google user or the mail will bounce post-cutover.

Plan for contacts and calendars#

Before you change anything else, log into the IONOS webmail with one of the users and export their contacts as vCard and their calendar as iCal. This is a per-user action that the user typically does themselves, but you should validate the path works before cutover. Google imports vCard and iCal directly via Contacts → Import and Calendar → Settings → Import & Export.

IONOS-side prep#

Confirm IMAP is enabled#

IMAP is on by default for IONOS mailboxes but can be disabled per-user. Log into the IONOS control panel, navigate to Email → User → Settings, and confirm IMAP is enabled. While you're there, check whether 2FA is on — that affects credentials.

Capture credentials#

For mailboxes without 2FA, the IMAP password is the mailbox password. For mailboxes with 2FA, generate an app-specific password from the user's IONOS account under Security → Application Passwords. Store everything in a password manager.

The IMAP connection details:

• Host: imap.ionos.com
• Port: 993
• Security: SSL/TLS
• Username: full email address (e.g., info@example.com)
• Password: mailbox password or app password

Lower DNS TTL#

24 hours before cutover, drop the MX TTL to 300 seconds in the IONOS DNS panel. The IONOS default is 3600 (1 hour), which means worst-case stale routing for a full hour after MX flips. Lower TTL = tighter cutover.

If you're new to MX and DNS propagation specifics, the MX record entry in our glossary covers the basics.

Choose your tool#

Google Data Migration Service#

Free. Built into the Workspace admin console. IMAP source, Gmail destination. Suitable for IONOS-sized mailboxes because they're typically small.

Limitations: no delta sync, single-threaded per mailbox, error messages are sparse, skips messages over 35 MB. Fine for small migrations; frustrating at scale.

Desktop IMAP tool#

Run a tool locally that does IMAP-to-IMAP between IONOS and Google. This is the Mailbox Taxi model. Desktop gives you concurrency control (important because IONOS throttles), detailed per-message logging, and resumable syncs.

For organizations with 20+ mailboxes and any expectation of compliance reporting, the desktop path saves you from "we don't know why these 47 messages didn't migrate" conversations later.

Hybrid#

Bulk via DMS, delta via a desktop tool. The cost-free DMS run handles most of the data; the desktop delta sweeps stragglers and gives you an audit trail.

The general approach for any IMAP source is covered in our migrate IMAP to Gmail walkthrough — IONOS is just one IMAP source among many that follow the same pattern.

Step-by-step#

1. Pilot mailboxes

   Pick a light and a heavy mailbox. Run end-to-end. Verify folder counts, sent-item presence, non-ASCII folder names (if applicable), and timing. Note your per-GB throughput — you'll use this number to plan the bulk window.

   If a user has German folder names ("Gesendet" for Sent, "Entwürfe" for Drafts, "Papierkorb" for Trash), make sure your tool maps them to the Google equivalents (Sent label, Drafts label, Trash). Without a map, you end up with literal "Gesendet" labels sitting next to the proper Sent label, and users will hate it.

2. Run the bulk pre-sync

   48 hours before MX cutover, kick off the bulk migration. Cap concurrency at 2–3 threads per mailbox; IONOS will throttle harder than most providers.

   If you're migrating 20+ mailboxes, stagger their start times by 10 minutes each to avoid hammering IONOS from one IP. They have softer per-IP limits in addition to the per-mailbox limits; staggering keeps you well under both.

   Monitor for Too many simultaneous connections errors — they're recoverable but indicate you're pushing too hard. Drop concurrency further if you see them.

3. Set up a forwarder (optional but recommended)

   12–24 hours before MX cutover, set up an IONOS-to-Google forwarder on each mailbox. From the IONOS control panel: Email → Email Address → Forwarding. Forward to the matching Google address.

   This gives you belt-and-suspenders coverage — even before MX flips, new mail starts copying to Google. After MX flips, IONOS isn't receiving new mail anyway, so the forwarder just stops mattering.

4. Cut MX to Google

   At your cutover time, replace IONOS MX records with Google's published values. From the IONOS control panel: Domains → DNS → MX Records.

   Delete the existing IONOS MX (typically mx00.ionos.com, mx01.ionos.com, etc., or older mx.kundenserver.de variants for grandfathered accounts). Add Google's MX records (priority 1: smtp.google.com. for current tenants — copy from the admin console for your tenant's exact values).

   Verify propagation with dig MX yourdomain.com @8.8.8.8. Send a test message from an external account.

5. Run the delta sync

   48 hours after MX cutover, run a delta against each IONOS mailbox. Any mail that landed during the propagation window gets pulled into Google. UID-based dedup keeps existing migrated messages from duplicating.

   This is the last bulk-data step. After this, no new mail should be landing at IONOS.

6. Import contacts and calendars

   Each user exports their IONOS contacts as vCard and calendars as iCal from the IONOS webmail, then imports into Google Contacts and Google Calendar. This is genuinely a per-user task — it can't be done en masse without each user's credentials.

   If you can't get users to do it, you can do it for them by logging into their IONOS webmail with their credentials and doing the export/import yourself. Most users prefer to do it themselves.

7. Update SPF, DKIM, DMARC

   SPF: replace IONOS includes with include:_spf.google.com. Full record: v=spf1 include:_spf.google.com ~all.

   DKIM: enable Google-managed DKIM from the Workspace admin console (Apps → Gmail → Authenticate email). Google generates the public key; paste it as a TXT record at google._domainkey.yourdomain.com in the IONOS DNS panel.

   DMARC: start with v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com at _dmarc.yourdomain.com. Monitor reports for a week, then tighten to p=quarantine or p=reject once reports look clean.

8. Cancel IONOS email

   After 30 days of clean operation, cancel the IONOS email service. Don't cancel sooner — you may discover a forgotten alias or missed message in the first month, and you want the source still accessible.

   Keep the IONOS domain registration if you like (it's independent of the email service). Or transfer the domain out to Google Domains, Cloudflare, or another registrar.

Failure modes you'll hit#

Too many simultaneous connections#

IONOS's per-mailbox connection ceiling is around 5. Drop concurrency. The error doesn't permanently lock the account, but it does throttle for 5–10 minutes. Retry loops without backoff make it worse.

Folder UTF-7 conversion errors#

If your tool doesn't speak modified UTF-7, folder names with German umlauts or French accents will appear mangled on the Google side: "Gesendete Objekte" becomes "Gesendete &AOk-bjekte" or similar. Modern tools handle this correctly. Verify your pilot mailbox includes a folder with non-ASCII characters before you trust the bulk run.

Stale 1and1.com records in SPF#

Older IONOS customers often have include:1and1.com or include:_spf.1and1.com in their SPF record. Remove these when updating SPF for Google. Stale includes don't cause hard failures, but they bloat the SPF lookup count and can push you over the 10-DNS-lookup limit, which is a soft fail.

Messages over 35 MB#

Google's inbound size limit. Anything over 35 MB will be rejected at the destination. Log them. Typical Bluehost-IONOS-shared-hosting mailboxes don't have many — usually a handful of old PDF training docs or oversized image attachments.

Domain mismatch between IMAP server and user#

If the IONOS user's email address doesn't match the domain on imap.ionos.com's certificate (e.g., the mailbox is info@example.com but imap.ionos.com is the cert), most tools handle this fine because they validate against the host, not the username. If you see a cert error, double-check you're connecting to imap.ionos.com and not an old imap.1and1.com address that may have been deprecated.

Comparing to other destinations#

For organizations evaluating Microsoft instead of Google, the IONOS to Office 365 path uses Microsoft's IMAP migration tooling and is roughly equivalent in effort. For single-user migrations, the IONOS to Gmail walkthrough skips the Workspace tenant setup.

For a broader view of destination tradeoffs, our Google Workspace migration guide compares the major options including cost, admin overhead, and feature parity for European-based users where data residency may matter.

Validation checklist#

Per-user:

• Folder counts match (Google labels vs IONOS folders, accounting for known maps).
• Message count per folder within 1% of source.
• Sent items present and ordered.
• Non-ASCII folder names appear correctly.
• Mobile clients picking up the new account.

Per-tenant:

• SPF record published, includes Google, excludes IONOS, under 10 lookups.
• DKIM signing outbound mail (check headers).
• DMARC reports arriving.
• All aliases recreated.
• All forwarders recreated (as Google routing rules or per-user filters).
• Catch-all behavior tested if applicable.

When both checklists pass, you're done. Wait 30 days, then cancel IONOS email service. Keep the domain or transfer it — your call.