As part of complying with security best practise we have converted ‘shared’ regular mailboxes to shared mailboxes. A key requirement is to enable shared mailbox to be set as default and to enable mail sent from SM to go to the SM Sent Items folder.

Part of the process is to add the SM under File/Account Settings/Account Settings/New but because these have been used before, the credentials have been stored and auto discovery then prevents the option to ‘Sign in with another account’ on the password pop up… as documented by Microsoft… see section 2d:

https://learn.microsoft.com/en-us/outlook/troubleshoot/profiles-and-accounts/add-shared-mailbox-as-additional-account

These are the things I have tried to:

Removed any previous ost and auto discovery xml files linked with the converted mailboxDisable Auto-Mapping using Exchange Online PowershellCleared Cached CredentialsCleared any previously saved identities in the registry
HKEY_CURRENT_USERSoftwareMicrosoftOffice<version>CommonIdentityCreated New Outlook profileReset AutoDiscover Settings (outlook.exe /resetnavpane)Disable AutoDiscovery (reg tweak)Disabled Simplified Account Creation (reg hack)Checked for Outlook updates

I have proved this works with a MS engineer last night on a fresh laptop account but I really need to fix existing user accounts.

I just can’t seem to be able to add the SM with a users account!

Any magicians out there that can suggest something?

I’m beginning to think this is a bug

​As part of complying with security best practise we have converted ‘shared’ regular mailboxes to shared mailboxes. A key requirement is to enable shared mailbox to be set as default and to enable mail sent from SM to go to the SM Sent Items folder.Part of the process is to add the SM under File/Account Settings/Account Settings/New but because these have been used before, the credentials have been stored and auto discovery then prevents the option to ‘Sign in with another account’ on the password pop up… as documented by Microsoft… see section 2d:https://learn.microsoft.com/en-us/outlook/troubleshoot/profiles-and-accounts/add-shared-mailbox-as-additional-account These are the things I have tried to:Removed any previous ost and auto discovery xml files linked with the converted mailboxDisable Auto-Mapping using Exchange Online PowershellCleared Cached CredentialsCleared any previously saved identities in the registryHKEY_CURRENT_USERSoftwareMicrosoftOffice<version>CommonIdentityCreated New Outlook profileReset AutoDiscover Settings (outlook.exe /resetnavpane)Disable AutoDiscovery (reg tweak)Disabled Simplified Account Creation (reg hack)Checked for Outlook updatesI have proved this works with a MS engineer last night on a fresh laptop account but I really need to fix existing user accounts.I just can’t seem to be able to add the SM with a users account!Any magicians out there that can suggest something? I’m beginning to think this is a bug  Read More

​