Writing a letter?

Question

css

Hello. Tell me please, I decided to create a letter in html for mailing,
1) as I understand it, css is stored only in tags?
2) where to store pictures
3) is it possible to use flex, or do I need to typeset on tables?
Thanks

Answer 1

1) yes
2) in external sources there is a picture, in a letter in img src just a link to the picture
3) tables

Answer 2

I will add that it is better not to use compound properties, for example padding, background use padding
-left , padding-right , background-image , background-position instead of them