Final answer:
Thanksgiving is not traditionally included in the introduction of a letter; it is usually found toward the end as a closing courtesy.
Step-by-step explanation:
The part that is NOT traditionally included in the introduction of a letter is thanksgiving. In a standard letter format, the introduction consists of the return address, the date, the inside address, and a greeting. The author's name is not typically in the introduction as well, however, it is typically found in the closing, where the letter is signed. The introduction will often have the subject line which represents the purpose of the letter.
Typically, the purpose is clearly stated at the beginning of the body to inform the recipient why they are receiving the letter. Thanksgiving, or expressing gratitude, is generally found towards the end of the letter, specifically in the last body paragraph or in the closing, as a way to thank the reader for their time.