Is the correct grammar than you for letter of or thank your dated?

The correct grammar for a formal letter or email is "Thank you for your letter/email dated..."

Here's why:

* "Than" is used for comparisons, while "then" indicates sequence.

* "Thank you for" is the correct phrasing for expressing gratitude.

* "Dated" is the proper word to describe a document's date.

Example:

"Thank you for your letter dated August 15, 2023."