If you are one of the Microsoft Teams enthusiasts and started using Teams from its early stage, you have ended up with many similar or unintended email IDs in your Outlook GAL. For each Team, Office 365 creates its own group’s email ID and it used to make the email ID available in the GAL.
After some noise in the User Voice, Microsoft stop showing those email IDs in the GAL by default. But if you already have many group email IDs showing in your GAL that you want to hide, use the following code snippets:
https://gist.github.com/AnupamRanku/7d1957dc11678100cb95ccdaba611913.js
Anupam Ranku 