[header] How to start a thank you letter [title] Start with a basic header. [step] It's hard to go wrong with a simple " dear susan, " as the introductory address of your message. If for some reason this feels inappropriate, it's also acceptable to simply begin with a name. 
The most important thing is that the recipient be able to see right away that the letter is intended for their eyes. [substeps] Though they're a more traditional method of correspondence, thank-you letters aren't inherently formal, so there's no need employ overly proper language.