>>Hello all,
>>
>>I know I can add CSS directly into an HTML page.
>>
>>I have to send emails and I would like to make them prettier.
>>
>>How do I add images directly in my HTML + CSS?
>>
>>Regards
>
>Check:
>
>https://mailtrap.io/blog/embedding-images-in-html-email-have-the-rules-changed/

Nice page. Except it does not list the main reason to block external pictures.
External pictures are used to trace, in special by spammers. One just give the linked file a name distinct to to receiver and will see if the email is read. This validates the mail for spamers. Else it's use by any data-gatherer.
So sane people will never load external stuff linked in an email.
(Or use something like Mailtrap that analyses incoming mail for own purpose)

Just my 0,02€cent