The basic structure for unsolicited sales letter usually has four parts, commonly known as the AIDA formula for sales presentation.
A – Attracting the readers’ favourable attention.
I – Arousing the reader’s interest.
D – Creating desire and convincing the reader.
A – Making clear the action the reader needs to take.
These parts (also known as functions of sales letter need not always be in the sequence they are listed above, nor need all parts be in every letter).