Signature in Mail make effective conversation for easy to identify when receiver seen your old mail in future, in fact you have to set perfect signature like name, your Website, company name, Social profile and any other in place of default text like sent from my iPhone or sent from my iPad for iPhone and iPad respectively. Now you can and you mush have to change signature or default text from your mail app. Not easy for all users to change signature but you can do easily from setting app from your iPhone, iPad with iOS 8/ iOS 9. Follow the below steps carefully for Change iPhone mail signature without and programming knowledge or without any third party application.
Steps for change iPhone mail signature: sent from my iPhone/ iPad: iOS 8/ iOS 9
Change signature: sent from my iPhone from iCloud, Microsoft Exchange, Google, Yahoo, Aol and Outlook.
Step 1: Go to the setting app from your iOS device (iPhone, iPad and iPod Touch)
Step 2: Then, Tap on Mail, Contacts, Calendars.
Step 3: Next, Tap on signature (Labeled with Sent from my iPhone) under the Mail, Contacts, Calendars option.
Update signature in Mail App from sent from my iPhone
Now you can see updated signature when you want compose new mail in iCloud Mail or Gmail Mail by switching from Mail app.