I'm looking for a way to use the common public emails such as Google and Yahoo and to prevent them from reading the content of the emails either by application that scans the emails and offer ads or manually to go the email and read it. Is there a way to do it only in the sender or receiver side. It means that I won't need the people that receive or send emails from me/ to me to install software in their side?
ProtonMail, https://protonmail.com, might be something similar to what you want to achieve. It offers an end-to-end encryption and works with other popular mail providers as well.
Your whole mailbox is encrypted with a private key that only you know of so no one, according to ProtonMail, can access your mailbox but yourself.
You can set an expiration time and password to emails sent to the third party email providers such as Gmail or Yahoo, meaning your recipient will have to know the password that you exchanged with in order to open your email.
The only way you would be able to prevent your email provider from reading your email content is to encode it, that is to change it from its original. You could use an encryption software, however that would require software running on both sides. There is free software out there to do this, but it requires that the sending and receiving sides use a common protocol.
You could change the content of the email my using some sort of code, like a markup language or word substitution which is know by both sides. This would hide the intention of the message but still be readable by the email provider. Any ads you get would be based on the text in the message. This would be a lot of trouble to implement, and again require both sides to be involved.
I suppose you could write a self-contained program which would run without requiring software to be installed on the recipient's computer. It could contain an encrypted message and have decryption software built-in. That would prevent the content from being automatically scanned.
Free email services make money by offering ads, if you want add-free email then use a paid service which promises not to read your email.