Migrate from GMX and Mail.com to JustEmails: Step-by-Step IMAP Guide

Looking to migrate from GMX and Mail.com to a real custom-domain inbox? The email bounced at 2 AM. A client contract sitting in their spam folder — flagged because the sending domain had no DKIM signature.

We were using GMX's free tier with a forwarding hack. Looked professional enough on the surface. But behind the scenes? No SPF we controlled, no DKIM, no DMARC. Just vibes and hope. The ad-supported email model doesn't care about your deliverability. It cares about showing you banner ads.

Here's the thing — GMX and Mail.com work fine for personal email. Forward your newsletters there, use the free storage, whatever. But the moment you're sending business email from a custom domain, you're playing with fire. No authentication control means ISPs treat your mail like it might be spoofed. Because from their perspective, it might be.

We're the JustEmails team — built by Velocity Digital Labs, the same folks behind ClickzProtect and JustAnalytics. We've walked a lot of people through this exact migration. GMX to something real. Mail.com to something they actually control. If you're coming from Google's ecosystem instead, check our Google Workspace migration guide.

This tutorial covers the full process: exporting your mail, pointing DNS, setting up authentication, and verifying everything works before you cancel the old account.

What You'll Have at the End

A custom domain inbox on JustEmails with full IMAP/SMTP access, all your historical mail migrated, and proper SPF/DKIM/DMARC records you control. Mail that actually lands in inboxes instead of spam folders. And a bill of $49/year instead of whatever GMX Premium charges for partial DNS access. See our comparison of flat-fee vs per-mailbox pricing to understand why this matters for teams.

Prerequisites

Before you start, you'll need:

• Your GMX or Mail.com login credentials
• Access to your domain's DNS (if GMX/Mail.com manages DNS, we'll cover transferring control)
• A JustEmails account — start the 7-day free trial if you haven't
• A machine with imapsync installed (macOS, Linux, or WSL on Windows)
• About 2 hours of hands-on time spread over 3-5 days

If your domain is registered through GMX or Mail.com directly, you'll want to transfer it to Cloudflare or Namecheap first. It's not technically required — you can update MX records in their panels — but their DNS interfaces are clunky and the fewer dependencies on ad-supported services, the better. (We learned this one the annoying way. Twice, actually. Don't ask.)

Budget your sending volume for the first two weeks as well. The per-account cap is 20/day for the first week, 200/day in the second, and 500/day from day 15 on, with mailbox sends and API sends counted against the same number. Warm-up is measured from domain verification rather than signup, so the domain you add here begins at the bottom of that ramp even on an account you've had for years. The IMAP export is unaffected — this governs outbound mail after the cutover.

Step 1: Check Your Current Setup

Log into your GMX or Mail.com account. Find the settings for your custom domain — usually under Settings → Email → Domains or something similar. Write down:

• The exact email addresses you're using
• Whether GMX/Mail.com manages your DNS or you point records at them externally
• Any aliases or forwarding rules

GMX's interface has changed at least three times in the past two years, so the exact menu path varies. Poke around. The information exists; they just hide it.

If you're on the free plan without custom domain support, you're probably forwarding a domain email to a @gmx.com or @mail.com address. In that case, there's no mail to migrate from GMX — your mail lives wherever it was forwarded from. Just set up JustEmails and point your domain there directly.

Step 2: Set Up JustEmails

Create your JustEmails account if you haven't. Add your domain — the dashboard guides you through verification with a TXT record. Takes about 5 minutes.

Then create mailboxes for every address you're migrating. Match them exactly: if you're using contact@yourbusiness.com on GMX, create contact@yourbusiness.com on JustEmails.

JustEmails gives you unlimited mailboxes on the $49/year plan, so create everything you need. Aliases, catch-alls, whatever. No per-mailbox fees to worry about.

Write down (or export) the IMAP/SMTP credentials for each mailbox. You'll need them for the migration and for updating your mail clients later.

Step 3: Export Mail via IMAP

Here's where imapsync does the heavy lifting. It copies mail between IMAP servers while preserving folder structure, dates, and read/unread status.

Install it:

# Ubuntu/Debian
sudo apt update && sudo apt install imapsync

# macOS
brew install imapsync

GMX's IMAP server is imap.gmx.com (port 993, SSL). Mail.com uses imap.mail.com (same port and settings). The command:

imapsync \
  --host1 imap.gmx.com --port1 993 --ssl1 \
  --user1 "you@gmx.com" --password1 "your-gmx-password" \
  --host2 mail.justemails.app --port2 993 --ssl2 \
  --user2 "you@yourdomain.com" --password2 "justemails-password" \
  --automap

For Mail.com, swap imap.gmx.com for imap.mail.com. Everything else stays the same.

If you're migrating multiple addresses, write a quick bash script or CSV loop. (We covered this in our Google Workspace migration guide — same pattern works here.)

Let imapsync run. A typical mailbox with a few thousand messages takes 30-90 minutes. Larger archives take longer. The tool is resumable — if it crashes, just run it again.

One thing: if GMX/Mail.com has rate limiting enabled (some accounts do), you might see connection throttling. Add --sleep 1 to the command to pause between operations. Slower, but reliable.

I'll be honest — watching imapsync tick through thousands of messages isn't exciting. Go make coffee. Or lunch. Or take a walk. It'll still be there when you get back.

Step 4: Lower Your MX TTL

Before changing MX records, drop the TTL (time-to-live) on your existing records. If you're managing DNS through Cloudflare, Namecheap, or similar:

1. Find your MX records
2. Change TTL from the default (often 3600 or 86400) to 300 seconds
3. Save and wait 24 hours

This matters. The old TTL has to expire across the internet before the new short TTL takes effect. Skip this step and you'll have mail routing to GMX for hours after you thought you cut over.

During this wait, go grab the JustEmails DNS records from your dashboard. You'll see one MX record, an SPF record, DKIM CNAMEs, and DMARC guidance. Screenshot or copy them somewhere accessible.

Step 5: Update DNS Records

Day of the cutover. Take a breath.

MX Record

Delete your existing MX records pointing to GMX (usually something like mx00.gmx.net or mail.gmx.com). In their place goes a single JustEmails record:

mail1.justemails.app (priority 10)

GMX hands you a stack of MX rows, so one line feels thin. It's all there is — one inbound host. Don't invent a second row at priority 20 to fill the gap; a backup MX pointing at a name that doesn't resolve delays inbound mail instead of protecting it. Check your JustEmails dashboard for the exact value.

SPF Record

Find your TXT record for SPF. If GMX set it up, it might include their servers:

v=spf1 include:_spf.gmx.net ~all

Replace it with:

v=spf1 a:mail1.justemails.app ~all

GMX gave you an include:; ours is an a: mechanism, which authorises the IP that mail1.justemails.app resolves to directly rather than chasing a second lookup. If you send through anything else — Mailchimp, a billing provider, your own app — keep their includes on the same line.

One SPF record only. Multiple SPF records break validation. I've seen this mistake made by people who definitely should know better. (Including, once, me.)

DKIM Records

Add the CNAME records JustEmails provides. They look like:

je1._domainkey.yourdomain.com → je1.dkim.justemails.app
je2._domainkey.yourdomain.com → je2.dkim.justemails.app

Delete any old GMX DKIM records if they exist. Most free-tier GMX setups won't have them.

DMARC

Most people skip this step.

Don't be most people.

If you don't have a DMARC record, add one:

v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

Start with p=none during migration. Once you've verified authentication is working, you can tighten to p=quarantine or p=reject. Our guide on ramping DMARC to p=reject safely covers the progression — don't skip this step if you care about deliverability.

Step 6: Verify DNS Propagation

Don't trust "instant" updates. Check with MXToolbox:

https://mxtoolbox.com/SuperTool.aspx?action=mx:yourdomain.com

You should see the one JustEmails MX host and nothing else. Check SPF and DKIM lookups too. If anything shows old GMX values, wait longer.

Send a test email from an external account (Gmail, Outlook, whatever you've got) to your migrated address. Verify it arrives in JustEmails, not GMX.

Step 7: Run Delta Sync

Any mail that arrived at GMX between your initial export and the MX cutover is still sitting there. Run imapsync again:

imapsync \
  --host1 imap.gmx.com --port1 993 --ssl1 \
  --user1 "you@gmx.com" --password1 "your-gmx-password" \
  --host2 mail.justemails.app --port2 993 --ssl2 \
  --user2 "you@yourdomain.com" --password2 "justemails-password" \
  --automap

Same command. imapsync only copies new messages. This delta sync usually finishes in minutes.

Step 8: Update Mail Clients

Your email apps need new server settings:

IMAP (incoming):

• Server: mail.justemails.app
• Port: 993
• Security: SSL/TLS
• Username: your full email address
• Password: JustEmails password

SMTP (outgoing):

• Server: mail.justemails.app
• Port: 587
• Security: STARTTLS
• Username: your full email address
• Password: JustEmails password

Outlook, Apple Mail, Thunderbird, your phone — update them all. Some mail clients cache credentials aggressively; you might need to remove the account and re-add it. (Looking at you, iOS Mail. Why do you make this so hard?)

Common Errors and Fixes

imapsync connection refused

GMX might be blocking automated IMAP access. Check if your account requires an "app password" or has external IMAP disabled. Look in Settings → Security → External access. If it's off, turn it on.

SPF failures after cutover

You probably have two SPF records, or the old GMX include is still in there. SPF allows one record per domain. Use MXToolbox to check:

https://mxtoolbox.com/spf.aspx

If it shows multiple records or syntax errors, fix them.

DKIM still shows old keys

DNS propagation. Wait an hour, then check again. If the CNAME records look correct in your DNS panel but MXToolbox doesn't see them, it's caching. Try a different lookup tool or wait longer.

Mail going to spam after migration

Check all three: SPF, DKIM, and DMARC alignment. Use Google's email headers analyzer or Mail Tester (https://www.mail-tester.com) to see what's failing. Usually it's a misconfigured SPF record or missing DKIM.

Next Steps

Keep GMX active for 2-4 weeks after cutover. Run imapsync one more time at the end to catch any stragglers. Then cancel.

Once your mail is flowing cleanly, consider:

• Tightening DMARC to p=quarantine then p=reject — our DMARC guide walks through this
• Setting up the JustEmails transactional API if you need programmatic sending — 1,000 emails/month included (see SMTP vs API for transactional email)
• Setting up per-client mailboxes and aliases on the domains you manage, so each client's mail lands in its own box under one unified inbox
• Comparing JustEmails vs Microsoft 365 if you're evaluating other alternatives

The ad-supported email model was fine for 2010. It's not fine for business email in 2026. You're sending contracts, invoices, client communications — and ISPs are increasingly skeptical of unauthenticated mail. Frankly, I'm surprised GMX still exists in this form. The $49/year is worth it just for the deliverability improvement, never mind losing the banner ads.

Real talk: the hardest part of this migration isn't technical. It's convincing yourself to spend the afternoon doing it instead of kicking the can down the road. But the next time a client email bounces because your domain has no DKIM signature, you'll wish you had.

Frequently Asked Questions

Can I migrate my custom domain from GMX to JustEmails?

Yes. GMX offers custom domain email on paid plans, but you own the domain. Point your MX records to JustEmails, update SPF/DKIM/DMARC, and use imapsync to pull over existing mail. GMX doesn't lock your domain — they just control the DNS while you're with them.

Does JustEmails work with domains purchased through Mail.com?

If you bought a domain through Mail.com and they manage DNS, you can either transfer the domain to a registrar you control (Cloudflare, Namecheap) or update MX records in their panel. We recommend transferring — it gives you full control over DNS records without Mail.com's interface restrictions.

Will I lose emails during migration from GMX?

Not if you keep GMX active during the transition. Export all mail via IMAP before cutting over MX records. Run a delta sync after cutover to catch anything that arrived in the gap. Plan 3-5 days for the full process.

Why can't I use SPF and DKIM properly on GMX's free plan?

GMX's free ad-supported plan doesn't give you DNS control for your sending domain. You're sending from their infrastructure with their authentication. Paid plans offer custom domain support, but the configuration options are limited. JustEmails auto-generates SPF, DKIM, and DMARC records you control.

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