dear sir vs dear madam

Dear sir, I hope this message finds you well.

I am writing to you, dear sir, regarding the recent changes in our project.

Thank you for your prompt response, dear sir, it is greatly appreciated.

As per our last conversation, dear sir, I have attached the necessary documents.

I would like to schedule a meeting with you, dear sir, to discuss further details.

Your guidance is invaluable, dear sir, and I look forward to your insights.

Please let me know if you require any additional information, dear sir.

I appreciate your attention to this matter, dear sir, and await your reply.

It was a pleasure meeting you last week, dear sir, and I hope to collaborate soon.

Thank you once again for your support, dear sir, it means a lot to me.