What most naturally follows?

How to write an office letter
Decide what format you will be using.
There are three popular formats to use: block, modified block, and semi-block. Block format means that all elements of the letter are aligned to the left of the page, modified block allows for some elements to be shifted to the right, and semi-block is aligned left but each paragraph is indented.
Block format is the most formal and widely used format. If you are unsure of what type of format to use, this is the best choice.