Hello Elvin Khunt,
Welcome to the Microsoft Q&A and thank you for posting your questions here.
Problem
I understand that you would like to have a webhook, or event trigger to send greeting message to users from your bot when they open MS team application.
Solution
Yes, you can trigger an event when a Microsoft Teams bot is opened by utilizing the conversationUpdate activity type. This activity is sent to the bot when a user starts a new conversation with the bot or adds the bot to a team.
To send a greeting message to a user when they open the Microsoft Teams application and interact with your bot, you need to handle the conversationUpdate activity. This activity is triggered in various scenarios, including when the bot is added to a team or a user starts a new conversation with the bot. However, there is no direct way to detect when a user opens the Teams application itself, as Teams does not provide an event for that specific action.
Accept Answer
I hope this is helpful! Do not hesitate to let me know if you have any other questions.
** Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful ** so that others in the community facing similar issues can easily find the solution.
Best Regards,
Sina Salam