[users] saving and sending as an attachment

[gary gangwisch]

dear sir/madam:
after writing a letter, i want to save to documents. i put in my own file name, 
under that is save as type. there are about 12 choices. could you tell me the 
best one to use?
i sent an e-mail w/attachment, they could not open it.
thank you for your support.  gary.