How to create a new user in deHOSTED Hybrid Exchange

Applies to: Exchange Online, Hosted Exchange, deHOSTED Exchange, deHOSTED Hybrid Exchange

Purpose

This article describes the correct procedure for creating a new user in a deHOSTED Hybrid Exchange environment.

If the order described below is followed, the Exchange object will be created correctly and the mailbox will be reachable both internally and externally.

Important note

To prevent email delivery issues from external senders, the mailbox must be created first via the deHOSTED Control Panel.

It is essential to select the mailbox type "O365 Mailbox".

The Microsoft 365 license should only be assigned after synchronization has completed.

Correct order for user creation

Step 1 – Create the mailbox in the deHOSTED Control Panel

Create the user or mailbox in the deHOSTED Control Panel.

Important: Select the following type:

O365 Mailbox

This ensures the mailbox is correctly prepared for hybrid or Exchange Online usage.

Step 2 – Assign the user to the AADC group

Assign the user to the AADC group.

This group ensures that the user is synchronized to Microsoft 365.

Step 3 – Wait for synchronization

Wait until Azure AD Connect synchronization has completed.

Only after synchronization is finished will the user object be fully available in Microsoft 365.

Step 4 – Assign the Microsoft 365 license

Now assign the appropriate Microsoft 365 license (for example Exchange Online or a Microsoft 365 plan including Exchange).

Recommended procedure

1. Create mailbox in deHOSTED Control Panel
2. Select mailbox type "O365 Mailbox"
3. Assign user to AADC group
4. Wait for synchronization
5. Assign Microsoft 365 license

What should be avoided

The following order may lead to external email delivery issues:

1. Create user in Active Directory
2. Synchronize the user
3. Assign Microsoft license
4. Create mailbox afterwards

In this case, a valid Exchange recipient object may not be created.

Possible error message

550 5.1.10 RESOLVER.ADR.RecipientNotFound
Recipient not found by SMTP address lookup

This means that Exchange Online cannot resolve the email address in the directory.

Result

• The Exchange object is created correctly
• Synchronization to Microsoft 365 works properly
• The license is assigned at the correct time
• The mailbox is reachable internally and externally