It sounds like you have enabled the "Guest Access" feature in Teams, which allows external users to join your Teams. When this feature is enabled, some users may need approval to join the Teams. To disable this feature and allow all users to join the Teams without approval, you can follow these steps:
- Go to the Teams Admin Center.
- Click on "Teams" in the left-hand menu.
- Select the Team that you want to modify.
- Click on "Settings" in the top menu.
- Scroll down to "Guest Access" and toggle it off. If you don't want to disable Guest Access entirely, you can also modify the settings to allow certain domains or email addresses to join without approval.
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