Q: A copy has been placed in your out box the sender address @yahoo.co.in was rejected by the server

Hi Anwer faridi,

Welcome to the Apple Support Communities!

I understand that you are not able to send an email from Mail on your iPhone because it is rejecting the sender address is being rejected by the server. To begin the troubleshooting process for not being able to send email, I would suggest reading over and working through the suggested steps outlined in the "Relaying denied" or "Email address rejected by the server" section from the attached article below.

Get help with Mail on iPhone, iPad, and iPod touch - Apple Support

Best regards