Send email from shared email address not working in Outlook (Office 36 Business), replies do work

The issue you're experiencing with sending new emails from shared mailboxes in Outlook while being able to reply to emails may be related to the permissions or the configuration of the Outlook profile. Here are some points to consider:

1. Permissions: Ensure that the employee has both Full Access and Send As permissions for the shared mailbox. While it seems they have the necessary permissions, sometimes the permissions may not be correctly applied or may take time to propagate.
2. Outlook Mode: Since you mentioned that the problem does not occur in the new Outlook, it may indicate that the issue is specific to the classic Outlook configuration. The classic Outlook may have specific settings or cached data that is causing this issue.
3. Cached Exchange Mode: If the employee is using Outlook in Cached Exchange Mode, consider switching to Online Mode to see if that resolves the issue. Sometimes, Cached Mode can lead to synchronization issues with shared mailboxes.
4. DelegateSentItemsStyle Registry Value: You mentioned changing the DelegateSentItemsStyle registry setting. Ensure that it is set correctly according to the desired behavior for sent items. Setting it to 1 can affect how sent items are stored.
5. Profile Recreation: If the above steps do not resolve the issue, consider recreating the Outlook profile for the employee. This can help eliminate any corruption or misconfiguration in the existing profile.
6. Updates and Repair: Ensure that Outlook is updated to the latest version. Additionally, running a repair on the Office installation might also help resolve any underlying issues.

If the problem persists after trying these steps, it may be helpful to consult with your IT department or Microsoft support for further assistance.

Hi JJansen,

Thank you for posting your question in the Microsoft Q&A forum. 

From your description, it appears the issue is isolated to Classic Outlook for a single user, and we can likely rule out permission configuration because the granted permissions apply to the account and New Outlook does not exhibit the problem. However, to understand more clearly and provide the most accurate support, could you share the following:

• When the user attempts to send a new email from the shared mailbox in Classic Outlook, what exactly happens? For example: is there an error dialog (please include the exact message/NDR), or does the email stay in Outbox without sending?
• Beyond clearing cache and editing the registry, has the user tried signing out and back in, or creating a new Outlook profile?
• Has the user tested Classic Outlook on a different device to verify whether the problem is tied to the account or is specific to that workstation?

Looking forward to your input.

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I thought I've sent a reply but it still was in concept, but below is what I wrote:

We've reinstalled the whole pc and the problem is solved for now.

But when sending new mails before the email wasn't sent and just put in the outbox and stays there forever.

We didn't create a new profile and weren't able to test outlook on any other device unfortuantely.

I think when delete the complete microsoft installation including registry inputs this would've also solved the problem. Unfortunately,