Last updated: June 18, 2021
After adding an email account to Outlook for Windows (Outlook 2016, 2013, 2010 versions) you may experience the following:
Your email account name shows up as outlook_[long series of letters and numbers]@outlook.com in the Folder Pane and when composing emails using Outlook for Windows.
Recipients will also receive the email from the sender with the outlook_[long series of letters and numbers]@outlook.com format.
When recipients reply to the email, the email bounces and you may receive the message “Undeliverable message when you send Internet mail in Outlook.”
This issue can occur when you register a 3rd party email address (e.g., an email address that is not Outlook.com or Hotmail.com) for your Microsoft Account and don't use Outlook.com for sending and receiving email.
If you typically use an Outlook.com account for email, this issue can occur if there are multiple aliases on the account and the 3rd party email address is the primary alias. Please see the ALTERNATIVE WORKAROUND section below.
Set up your account manually as an IMAP or POP account in Outlook.
Use Windows Key + R then type “outlook /profiles” (omitting the quotes) in the Run window and hit “OK” Note: There is a space between outlook and the forward slash (/)
In the launched “Choose Profile” box, select Options > New
Type a new, unique profile name and select OK
Choose Advanced options > Let me set up my account manually.
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