Quote Originally Posted by Yuki View Post
Не прочитав письмо от мамы, он ушёл.
Is there any possibility that he had read some part of the letter before he left?
Imho, there is such possibility.

Не читав письмо от мамы, он ушёл. — he has read nothing in the letter
Не дочитав письмо от мамы, он ушёл. — he started to read but hasn't finished
Не прочитав письмо от мамы, он ушёл. — we don't know if he read some part of the letter or not