Transfer from One.com to Microsoft 365

Question

Hi,

Yesterday i wanted to transfer to m365 business.
So i started with getting a m365 business basic free trial and created a reroute from one.com to m365 so the new e-mails ended up in outlook.

After that i changed the m365 account to the existing domain so everything was linked to my business mail account.

I wanted to add the old emails to outlook but couldn't find a way.
I found that it was easiest to open both in outlook app trough imap but that wasn't possible on the basic business version. (only outlook web)

So i purchased the m365 copilot business standard.

Now i can't get on my mail account anymore on outlook so the support team can't reach out to me via mail.

Now everythings messed up, i can't call support and the help desk person who is asigned to my problem can't mail me. Well he can mail me but i can't see new mails. since they all get rerouted to outlook.

Can anyone please help me or know how i can get quick support trough a call? i'm Belgian so preferably a belgian help desk team.

Answer 1

Hi @Diequito Desmet, 

Thank you for posting your question in the Microsoft Q&A forum. 

Regarding the error code 500 you’re encountering, I’d like to ask a quick question to better understand your situation and assist you more effectively: 

Do you still have access to the Microsoft 365 admin center? 

If you do still have access, please verify that your account is assigned the correct license. Missing or incorrect Exchange Online licensing can often cause issues when transferring services or accessing email features. 

How to check your license assignment 

1. Sign in to the admin center: https://admin.microsoft.com/ using your admin credentials 
2. Navigate to Users → Active users 
3. Select your username 
4. Click Licenses and apps
5. Expand Apps and ensure that Exchange Online (Plan 1 or Plan 2) is enabled. 

This will help confirm that your account has the necessary permissions to proceed with the transfer and avoid the 500 error. 

Thank you again for your time and understanding. While my initial response may not resolve the issue immediately, I’d like to gather more details about your situation so I can assist you more effectively.         

I really appreciate your patience, and I’m here to help. Looking forward to your response.                                  

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Answer 2

To regain access to email and get support, use these steps:

1. Verify Outlook sign-in and profile
   • Open Outlook on the device.
   • If prompted, enter the Microsoft 365 Business account email address and password and select Connect.
   • If Outlook opens but shows the wrong mailbox or errors, create a fresh profile:
     • Open Control Panel → Mail → Show Profiles….
     • Remove any problem profiles.
     • Select Add…, give the profile a name, then enter the business email address and password and let automatic setup complete.
     • Start Outlook with this new profile and confirm that the correct Microsoft 365 mailbox opens.
2. Confirm the Microsoft 365 mailbox is working
   • Once Outlook opens with the correct profile, send a test email from the business address to an external address and reply back to confirm send/receive works.
   • If Outlook still cannot connect, sign in via Outlook on the web using a browser to confirm whether the mailbox itself is working. If web access works, the issue is local to the Outlook client and the profile recreation above is required.
3. Move old email from One.com to Microsoft 365 Once access to the Microsoft 365 mailbox is restored, import the old mail:
   • In the old mail environment (for example, an Outlook profile connected to One.com), export mail, calendar, and contacts to a .pst file:
     • In Outlook: File → Open & Export → Import/Export → Export to a file → Outlook Data File (.pst) and include subfolders.
   • Then import that .pst into the Microsoft 365 mailbox:
     • In Outlook: File → Open & Export → Import/Export → Import from another program or file → Outlook Data File (.pst) and select the exported file.
   • This moves historical email, calendar, and contacts into the new Microsoft 365 mailbox.
4. Get Microsoft 365 business support by phone
   • From a browser, sign in to the Microsoft 365 admin center with the admin account for the Business subscription.
   • In the bottom-left corner, select Help & Support.
   • In the Support Assistant pane, type a short description (for example, “request an agent to contact me via phone”) and press Enter.
   • At the bottom of the pane, select Contact support.
   • Choose Support via phone, fill in the required details (including a phone number that can be reached), and submit.
   • A Microsoft 365 technical support engineer will call back. Regional routing (including Belgium) is handled automatically based on tenant and contact details.

If the mailbox is still inaccessible after recreating the Outlook profile and confirming web access, use the admin center support flow above so that engineering can check the tenant and mail routing configuration.

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References:

• Set up Microsoft 365 Business Basic
• Set up and use Outlook
• Migrate data to my Microsoft 365 for business subscription
• Move your old email, calendars, and contacts to Microsoft 365
• Get support - Microsoft 365 admin | Microsoft Learn