Main user name on email doesn't receive emails Alias name still does affecting all emails in business

Malcolm Taylor 0 Reputation points
2026-09-12T07:40:44.6466667+00:00

Hi I need help how to resolve the issue with main usernames as our incoming emails are not coming through and throws up Entra ID issue but the Alias names attached works fine the AI support just gives me the run around

if some can provide a step-by-step fix I would really appreciate it

Outlook | Windows | New Outlook for Windows | For business
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  1. Muhammad Bilal Khan 0 Reputation points
    2026-09-12T08:02:30.14+00:00

    Hi @Malcolm Taylor
    The fact that the alias still receives mail is a useful clue. It suggests the mailbox itself is probably working, but the primary SMTP address may be incorrect, missing, or not syncing correctly through Entra ID.

    I’d troubleshoot it in this order:

    1. Check the mailbox in Exchange Admin Center Go to Exchange admin center → Recipients → Mailboxes → select the affected user → Email addresses. Make sure the address that should be the main email is listed as the primary SMTP address (shown in bold). Check for duplicate addresses If the primary address is also assigned to another user/contact/group, Entra synchronization can fail because SMTP proxy addresses must be unique. Check Entra ID → Users → Users with errors for a proxy-address conflict. If the users are synchronized from on-premises AD, don't fix the address only in the Microsoft 365 portal. Check the user's on-premises AD proxyAddresses attribute. The primary address should look like:
    SMTP:******@yourdomain.com

    Secondary aliases should use lowercase:

    smtp:******@yourdomain.com

    The uppercase SMTP: identifies the primary address.

    Run a sync and check for errors in Microsoft Entra Connect. If the primary SMTP address is being overwritten or moved to an alias, investigate the on-premises proxyAddresses and, in a hybrid environment, the targetAddress attribute as well. Microsoft documents cases where targetAddress can cause the primary SMTP address to be replaced.

    After correcting the address, allow synchronization to complete and test by sending a message from an external mailbox to the primary address. Also check the NDR/bounce message if one is generated.

    I would not delete/recreate the users or mailboxes yet. Since the aliases are working, there is a good chance this can be corrected by fixing the primary SMTP/proxy address or an Entra synchronization conflict.

    If you can post the exact Entra ID error message (with the domain/user details hidden), that would be the next thing I'd look at. It can tell us whether this is a duplicate proxy address, synchronization problem, or an Exchange recipient issue.The fact that the alias still receives mail is a useful clue. It suggests the mailbox itself is probably working, but the primary SMTP address may be incorrect, missing, or not syncing correctly through Entra ID.

    I’d troubleshoot it in this order:

    Check the mailbox in Exchange Admin Center
    Go to Exchange admin center → Recipients → Mailboxes → select the affected user → Email addresses.

    Make sure the address that should be the main email is listed as the primary SMTP address (shown in bold).

    Check for duplicate addresses
    If the primary address is also assigned to another user/contact/group, Entra synchronization can fail because SMTP proxy addresses must be unique. Check Entra ID → Users → Users with errors for a proxy-address conflict.

    If the users are synchronized from on-premises AD, don't fix the address only in the Microsoft 365 portal. Check the user's on-premises AD proxyAddresses attribute.

    The primary address should look like:

    SMTP:******@yourdomain.com

    Secondary aliases should use lowercase:

    smtp:******@yourdomain.com

    The uppercase SMTP: identifies the primary address.

    Run a sync and check for errors in Microsoft Entra Connect. If the primary SMTP address is being overwritten or moved to an alias, investigate the on-premises proxyAddresses and, in a hybrid environment, the targetAddress attribute as well. Microsoft documents cases where targetAddress can cause the primary SMTP address to be replaced.

    After correcting the address, allow synchronization to complete and test by sending a message from an external mailbox to the primary address. Also check the NDR/bounce message if one is generated.

    I would not delete/recreate the users or mailboxes yet. Since the aliases are working, there is a good chance this can be corrected by fixing the primary SMTP/proxy address or an Entra synchronization conflict.

    If you can post the exact Entra ID error message (with the domain/user details hidden), that would be the next thing I'd look at. It can tell us whether this is a duplicate proxy address, synchronization problem, or an Exchange recipient issue.

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  2. AI answer

    2026-09-12T07:40:58.9366667+00:00

    If the primary business address is not receiving mail but an alias still works, use this order of checks:

    1. Check whether mail is missing only in Outlook or missing from the mailbox itself
      • Sign in to Outlook on the web for the affected mailbox.
      • If messages arrive there but not in Outlook for Windows, the issue is the Outlook app or profile, not mail flow.
    2. Run Microsoft Support and Recovery Assistant on the affected PC
      • This is recommended for single-user Outlook or Microsoft 365 account issues.
      • It can detect profile and Outlook configuration problems.
      • Note: the Get Help troubleshooters are not available for new Outlook for Windows.
    3. If the user is synchronized from on-premises Active Directory, fix the alias there
      • If the account shows: “This user is synchronized with your local Active Directory. Some details can be edited only through your local Active Directory”, the address changes must be made on-premises.
      • Open Active Directory Users and Computers.
      • Turn on View > Advanced Features if needed.
      • Open the user account: Properties > Attribute Editor > proxyAddresses.
      • Add or correct the required address using the lowercase prefix smtp: for a secondary alias, for example smtp:******@contoso.com.
      • Then wait for the changes to sync to Microsoft Entra ID.
    4. If the tenant or custom domain was added recently, wait for setup to finish
      • If the error includes “A parameter cannot be found that matches parameter name EmailAddresses”, tenant or domain setup may still be completing.
      • Setup can take up to 4 hours.
      • Retry after that delay.
    5. If only one user is affected, verify Outlook profile behavior
      • If Outlook on the web works but Outlook for Windows does not, create a fresh Outlook profile or use Support and Recovery Assistant.
      • This helps rule out a corrupted local profile.
    6. If the mailbox still does not receive mail on the primary address after the above checks, contact support
      • If tenant setup delay is the cause and the issue persists, Support can perform a full sync.

    A practical way to isolate the problem is:

    • Primary address fails in Outlook on the web too: likely address or directory configuration.
    • Primary address works in Outlook on the web but not Outlook for Windows: likely Outlook client/profile issue.
    • User is directory-synced: update proxyAddresses in on-premises AD, then allow sync to Entra ID.
    AI-generated content may be incorrect. Read our transparency notes for more information.

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