Hi Limal,
Thank you for posting your question in the Microsoft Q&A forum.
Based on your description, I recommend reviewing these settings to confirm they are configured correctly.
1. In Microsoft Teams Admin Center
Access in Teams Admin Center with Administrator roles >Navigate to Teams > Teams Setting > Email Integration > Turn on "Users can send emails to a channel email address".
This step to allow users to send emails to Microsoft Teams channels
2. In Teams Channel
Go to the channel name on Teams, and select More options > Get email address > Advanced Settings
For your information: Link Article
Hope you will solve the problem soon
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.