Goal

Transforming guest user names from Azure AD so that they match Atlassian usernames.
A guest username in Azure looks like the below and a transformation will basically restore the email address part of the guest username. 

Prerequisites

• an Azure AD subscription

• A (evaluation) subscription for the SAML SSO app

• Admin access to your Atlassian product

For more information about the prerequisites listed above, access the following link:

https://wiki.resolution.de/doc/saml-sso/latest/all/setup-guides-for-saml-sso/azure-ad

Step-by-Step Guide

1. Go to the SAML SSO configuration page
   
   

2. Select your identity provider (#Image 01)
   
   

3. Scroll down to User ID Transformation
   
   

4. Uncheck The IdP's NameID Attribute Matches the User IDs in Jira
   
   

5. Then click Add one+ next to UserID transformation
   
   

6. Add the following transformation (#Image 02):
   Regular expression: (.*)_(.*)#EXT#.*
Replacement: $1@$2
   
   

7. Save your configuration.
   
   

Image 01: Select the entry for the Azure AD identity provider

Image 02: Add the following transformation