Last updated: May 7, 2018
After connecting to Outlook for Windows (Outlook 2016, 2013, 2010 versions) to your Outlook.com email account, your 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 only impacts customers using Outlook for Windows. Emails sent via Outlook.com on the web works correctly and emails will be sent with the correct email address.
The Outlook client does not currently support using a non Microsoft domain primary alias. For the time being to get the account to work in Outlook you need to change the primary alias to a Microsoft domain account, such as @outlook.com or @hotmail.com.. The Outlook Team is doing work that will enable some supported use of aliases in the near future. We will update this topic as soon as the functionality is available.
This issue occurs for users with multiple account aliases. We are actively working on a fix. In the meantime, to fix this issue, please do the following:
Note: If you do not have another alias, click the link on the page to create one "Click Add email and a new alias". Then choose the option "Create a new email address and add it as an alias"
Go to https://account.live.com/names/Manage and sign in to your Outlook.com account.
Set your Outlook.com email as the primary alias.
In Outlook for Windows, remove and re-add the account. See the steps in this article: Add your Outlook.com account in Outlook for Windows
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