Read part of a letter.

i'm looking forward to our fun in the sun this summer. for inviting us to come fishing on your boat. fishing is one of my favorite pastimes.

this part of a letter is called the

Why is it important to include a descriptive subject heading? it in sorting the topics. it the recipient see its importance. e-mail programs won’t allow e-mail to be sent without it. it keeps junk e-mail separate from important e-mail.