unable to send a mail even when my mail id is verified

@Keiji Otsubo @Berehane Shishaye @Supriya j.n I just wanted to come back and say thank you to everyone who took the time to help me with this issue.

I spent nearly a day trying to figure out why the email wouldn't send and was completely stuck. Your suggestions, explanations, and willingness to help pointed me in the right direction. The solution ended up being enabling the substitute email address for unverified domains in Deliverability, and after that I was finally able to complete the module successfully.

I really appreciate everyone who replied and shared their knowledge. As someone who's still learning Salesforce, having such a supportive community makes a huge difference. Thank you all for your time, patience, and kindness. Wishing you all the very best, and I hope I'll be able to help someone else in this community in the future, just as you helped me today. 😊