If you are using solely Gmail as your mail provider and work on your mails via the browser and the clients on the smartphones, our Plugin for Outlook is not for you. But there is help:
If you put sensitive information into your email created with gmail, you should create a protected ZIP file with 7zip before you upload the documents and attachments into the Google cloud.
We all know, that Google is automatically looking into the mails for advertising purposes and who knows if that will always work they way the developers intended!
The free 7zip tool is around for ages and has always been Open Source and free:
Note the password fields on the right.
So, our approach for sending encrypted emails with gmail is to protect the attachments with a password and to send the password to the receiver via WhatsApp or other means outside of the Google world (text message, phone call, etc.).
Even a short “1” as a pin code already hides anything in the archive from automated parsing and keeps robots out.
The longer the password is the better is the protection for your attachment, but the best encryption for gmail is still using it with a modern email client (Outlook with our plugin or a PGP based method) and not via the browser interface.