Webmail: cannot receive email sent from public email providers

Hello,

Webmail accounts created can send and receive internal emails just fine.
They can also send external emails (to gmail or yahoomail). However, it cannot receive external emails.
Received the following error message in my gmail account:

Delivery has failed to these recipients or groups:

**************
The email address you specified couldn't be found or is invalid. It may be due to a bad entry in your Outlook or Outlook Web App recipient AutoComplete cache. Use the steps below to delete the entry from the cache:

Click New mail.
In the To field start typing the recipient's name or email address until the recipient appears in the drop-down list.
Use the DOWN ARROW and UP ARROW keys to select the recipient, and then press the DELETE key.
Then resend your message – delete and retype the recipient’s name or e-mail address before sending it.

For more tips on how to resolve this issue see DSN code 5.1.1 in Exchange Online.


Would anyone know how to fix this? Any help is greatly appreciated.

Thanks,
steven78