Hey there sreenath.yr,
I see that you are experiencing an issue with mail fetching on your iPhone. First, I would suggest that you make sure your “Fetch New Data” setting is adjusted too your preference. You can find this in your Settings app, under “Mail, Contacts, Calendars.”
Mail settings - iPhone
http://help.apple.com/iphone/9/#/iph5ca4d6a69
If this doesn’t resolve the issue, try the troubleshooting steps found in this article:
Get help with Mail on iPhone, iPad, and iPod touch - Apple Support
https://support.apple.com/en-us/HT201419
Take care, and thanks for visiting the Apple Support Communities.