Outlook Signature Update Agent prompts for credentials


The Outlook Signature Update agent prompts the user for credentials, but the credentials are not accepted and the prompt reappears.


One of the common causes for this issue is that the user has not signed into OWA for the first time.

For Signature Manager Office 365 Edition to deploy signatures and settings to a user’s OWA account (for either Exchange or Office 365), the user’s profile must have been created in OWA. This is known as ‘hydrating’ a user’s account.

A user’s profile is hydrated the first time they log on to OWA and select their regional options. It is not hydrated when a user accesses their mailbox using an email client such as Outlook - they must log on to the OWA website itself for the mailbox to be hydrated.


  • The user must sign into OWA for the first time and set regional options. Alternatively the account can be hydrated using PowerShell, as per this knowledge base article.

Note that:

  • Once the user has signed into OWA, please allow time for the signatures to be rebuilt before re-testing.
  • If the user has already signed into OWA and the issue is still occurring, please raise a support ticket.

Signature Manager Office 365 Edition Troubleshooting