Your email program is using outdated address information for ***********************

Hi,

Delete the Outlook Data Files (OST/PST): DONE

Clear Outlook's Forms Cache: DONE

I am still issues with sending emails. See : Undeliverable Consultation - Phil (LEAP Estates Support).msg

• This one autogenerated from Mybooking page at Microsoft Office 365 and it bounced. Seems something wrong with my email setup rather than outlook?

Hello Pavan Nagori,

Thank you for the follow-up and the detailed information about your setup. I'm glad we can continue working through this together, and it’s great to hear that sending from the web version of Outlook worked!

It looks like you’re still experiencing the issue when replying to emails in the desktop version of Outlook, even after clearing the Auto-Complete list and ensuring no contacts are saved. Since you're using an older email that was migrated from Google to Office 365, the problem may be linked to outdated email addresses embedded in legacy threads or replies, especially when using "Reply All."

You've already done a lot by clearing the Auto-Complete list, checking for contacts, and testing with the web version. That’s excellent troubleshooting on your part! Since the problem persists specifically in the desktop version when replying to migrated emails, I believe we’re getting closer to identifying the root cause.

Given that sending via Outlook Web works without any issues, here are some steps we can try to resolve the issue within the desktop version:

Clear Outlook's Forms Cache:
Since the issue may be linked to corrupted cached data, try clearing the forms cache.

1. Close Outlook.
2. Open Control Panel → Mail.
3. Click Data Files → Forms → Clear Cache.
4. Restart Outlook and try replying to the email again.

Delete the Outlook Data Files (OST/PST):
Outlook could still be holding onto outdated data. Deleting the data file can force Outlook to rebuild and correct any lingering issues.

1. Close Outlook.
2. Navigate to C:\Users\[Your Username]\AppData\Local\Microsoft\Outlook.
3. Locate and delete (or rename) the .ost file associated with your account. Don't worry—this will be recreated when you restart Outlook.
4. Open Outlook, let it resync with the server, and attempt to reply again.

Remove Specific Entries Manually

1. Start composing a new email.
2. In the To field, begin typing the recipient's name or email address.
3. When the outdated entry appears in the drop-down list, use the Down Arrow key to highlight it and press Delete.

Check for Cached Credentials

Outlook may be using cached credentials from your previous Google Workspace account. Try clearing the cached credentials:

1. Open Outlook.
2. Go to File > Account Settings > Account Settings.
3. Select your Office 365 account and click Change.
4. Click More Settings.
5. Go to the Security tab and click Clear Credentials.

Recreate the Outlook Profile:
Recreating the Outlook profile can often fix stubborn issues related to corrupted or outdated settings.

1. Open Control Panel → Mail.
2. Click Show Profiles and then Add to create a new profile.
3. Set the new profile as the default and open Outlook using this new profile.
4. Test the "Reply All" function and see if the issue is resolved.

Verify Email Addresses and Contacts

Ensure that you are using the correct email addresses for recipients. If they have changed their email addresses or left the organization, you may need to obtain their current email from another source.

Also, check if the contacts you are replying to are saved correctly in your Office 365 account. You can try creating a new contact or verifying the existing ones.

Workaround:

• If the issue only occurs when replying to emails that were originally sent or migrated from Google, you might want to manually type the email addresses for those recipients instead of using "Reply All."
• Since the web version works fine, you can also continue using Outlook on the web for these specific cases as a temporary workaround until the desktop issue is fully resolved.

If none of these steps resolve the issue, it's recommended to contact your IT department or email administrator for further assistance. They can perform more advanced troubleshooting and check for any underlying issues within your Office 365 environment.

It’s quite amusing that you received the same error while trying to reply to my message! Let's get this sorted so you can confidently reply to anyone without issues.

Please try the steps above and let me know how it goes. We’re here to assist you further if needed!

Appreciate your patience and understanding and thank you for your time and cooperation. Have a great day!

Sincerely,

Microsoft Community Moderator

Hi,

Version: Microsoft® Outlook® for Microsoft 365 MSO (Version 2408 Build 16.0.17928.20114) 64-bit

Business account:  ***********************

No error message – only the non-delivery email.

File  'streaming.dat' not found in  LOCALAPPDATA%\Microsoft\Outlook.

Empty Auto-Complete List ****-à  done again

Sending from Web version was successful !

Contacts – no saved.  I am using an older email migrated from Google to 365 and clicking on ‘REPLY ALL’

BTW, I got the same error message trying to reply to you email message! LOL

Hello Pavan Nagori,

Thank you for reaching out to the Microsoft Community Forum. Please accept our warmest regards and sincerest hope that all is well.

To address the issue you're experiencing with the IMCEAEX error in Office 365, it's important to understand that this error typically arises from outdated entries in the Auto-Complete List in Outlook. The error message indicates that your email program is using an outdated address for the recipient, which often occurs when the recipient's email address has changed or they have left the organization.Here’s a structured approach to resolve this issue:

You're encountering a non-delivery report (NDR) when replying to emails, indicating that your email program is using outdated address information for a recipient. The error message includes "IMCEAEX," which signifies that Outlook is trying to use a legacy email address that no longer exists.

You have already attempted to clear the Auto-Complete List in Outlook, which is a common first step in resolving this issue. However, it seems that this did not resolve your problem.

To better understand and investigate your issue,may I get some more detailed information from your side:

1. Will you please share me your Outlook version details? Please follow this article What version of Outlook do I have? - Microsoft Support and follow the steps to check.
2. Are you using Microsoft365 business account(@xxx.onmicrosoft.com/@yourdomain.com) or personal account (which is ended with outlook.com/hotmail.com/live.com/msn.com) or some other 3rd party pop/imap account?
3. Will you please share me any error screenshots? Clear cached Outlook data

• Close Outlook.
• Navigate to %LOCALAPPDATA%\Microsoft\Outlook.
• Delete the 'streaming.dat' file.

Clear Outlook Auto-Complete Cache Again You mentioned clearing the Auto-Complete List, but let's ensure it's done thoroughly:

• Open a new email in Outlook.
• In the To field, type the recipient’s name or email, and when the dropdown appears, press the Delete key to remove the suggested contact.

Clear the Auto-Complete List Again

Even if you've tried this before, it's worth ensuring that you are clearing the Auto-Complete List correctly. Here’s how you can do it:

1. Open Outlook.
2. Click on File > Options.
3. Select the Mail tab.
4. Under Send Messages, click on Empty Auto-Complete List and confirm by clicking Yes.

Alternatively, you can start Outlook with a command to clear the cache:

• Press Windows + R, type Outlook.exe /CleanAutoCompleteCache, and press Enter.

Remove Specific Entries Manually

If clearing the entire list does not work, you may need to remove specific entries:

1. Start composing a new email.
2. In the To field, begin typing the recipient's name or email address.
3. When the outdated entry appears in the drop-down list, use the Down Arrow key to highlight it and press Delete.

Try Sending from Outlook on the Web (OWA) This issue could be tied specifically to the Outlook client. Try sending an email from Outlook Web Access (OWA) to the recipient. Here’s how:

1. Log in to Outlook on the Web.
2. Start a new email and manually type the recipient's email address.
3. Send the email to see if it works without the IMCEAEX issue.

Delete and Recreate the Contact in Outlook

In case the recipient was modified in your Global Address List (GAL), their contact info might be outdated:

1. Delete the contact from your personal Outlook Contacts and then create it fresh with the correct email address.
2. Ensure that the email address is correct in both your personal contacts and the Global Address List.

Ensure Proper Addressing If the user has migrated or changed, make sure to use the correct email format in Office 365.

1. Go to your Global Address List.
2. Search for the recipient and use the updated, correct email address.
3. Try sending a new email.

Use Microsoft Support and Recovery Assistant:

• If issues persist, consider using Microsoft's Support and Recovery Assistant tool. This tool can help diagnose and fix various Outlook and Office 365 issues.Microsoft Support and Recovery Assistant (SaRA) 17.01.1903.000 - Download, Review, Screenshots (softpedia.com)

Domain and MX Records Check:

• Ensure that your domain is active and that your MX records are correctly configured. This can affect email delivery if not set up properly.

As an administrator, you may need to investigate deeper if the above doesn't resolve the issue. The "IMCEAEX" address format typically indicates legacy Exchange email addresses that Outlook is struggling with.

Verify Recipient's Email Address

Ensure that you are using the correct email address for the recipient. If they have changed their email address or left the organization, you may need to obtain their current email from another source (e.g., contacting them directly or checking with your IT department).

Run PowerShell Command to Update Addresses: Use PowerShell to check or update the user's email address or X500 address.

powershell
Set-Mailbox "User" -EmailAddresses @{add="X500:/o=EXCH/o=First Administrative Group/cn=Recipients/cn=UserName"}

Check for LegacyExchangeDN Issues

If the problem persists after clearing the Auto-Complete List and verifying email addresses, it may be related to LegacyExchangeDN issues:

• The IMCEAEX error indicates that Outlook is trying to deliver mail using an outdated LegacyExchangeDN attribute. You may need to create an X500 proxy address for any affected users whose addresses have changed.

To do this:

1. Identify the IMCEAEX address from your NDR message.
2. Convert it into an X500 address by following these steps:
   • Remove "IMCEAEX-" from the beginning.
   • Replace underscores (_) with slashes (/).
   • Replace "+20" with spaces.
   • Replace "+28" with "(" and "+29" with ")".
   • Remove any domain information at the end.
   For example: text IMCEAEX-_O=Domain_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_CN=Recipients_CN=******@domain.com would convert to: text X500:/O=Domain/OU=Exchange Administrative Group (FYDIBOHF23SPDLT)/CN=Recipients/CN=User

Use PowerShell to add this X500 address as an alias for the user who is not receiving emails.

Contact Your Email Administrator

If none of these steps resolve your issue, it may be necessary to involve your IT department or email administrator. They can check for any underlying issues within your organization's Exchange settings or perform more advanced troubleshooting.By following these steps, you should be able to resolve the IMCEAEX non-delivery report issue in Office 365 effectively.

By following these steps, you should be able to resolve the IMCEAEX non-delivery report issue in Office 365 effectively.

Please understand that our initial response may not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution.

Appreciate your patience and understanding and thank you for your time and cooperation. Have a great day!

Sincerely,

Microsoft Community Moderator