Enable dkim signing and TLS on local server

Hello people,

I’m not sure if Ghost can do such thing but it would be nice to enable DKIM and TLS for outgoing mail.
I’ve installed sendmail and successfully enabled DKIM on it which allowed the email to have this extra header only when sending emails using the console. Sending emails from ghost won’t use DKIM for some reason.

I’d like to know if it’s possible to use DKIM with sendmail or other software such as exim.
Can I also use the Let’s encrypt ssl with the email as well?

I’m sorry if the question is stupid. I don’t know a lot about ghost and this is the first time I use anything other than wordpress.

Thank you!