Question : email quality, email encryption

[MatthieuHPP]

Hello,

I am new to the use of sending emails via website, and I have implemented sendmail.
It works but and I am looking for ways to improve the quality of sent emails so as they are not seen as spams.

I will use use opendkim for this, and I would like to know if there is a way to active ssl / tls using sendmail ?

Many thanks

Matthieu