If a mail arrives for the first time in your inbox , and you click on the drop down arrows and click on add to contacts the complete mail address will be copied in the address book application , this is the way it works as new contact will be added because mail application treats this as a new contact for the first time .
You can see the mail address is added and not the first and last name , click on edit go the mail address it will be highlighted , take cursor to the extreme right and click on delete button two to three times or more to completely delete the address and type the desired name in the first and last , click on done to save the data .
And if the contact is already saved in the address book ( by clicking on edit button filling up the first name and last number , mobile number the primary single mail address and rest of credentials like street address etc ... and click on done the data will be saved in all contacts .
You must have an web mail account ( say gmail account and iCloud account ) already configured . Generally gmail id is kept same as Apple ID .
You have to verify by entering in system preferences > internet accounts > click on google all the boxes for contacts , notes ( 4 of them must be checked ) , and in I cloud all of the boxes are checked except back to my Mac .
And , if you want to add second mail address to the person name , already in address book , click on copy address and open address book > again click on edit > click on the work and paste ( command and V ) the mail address will be pasted .
And finally click on done to save the data .
