Google and similar tools are not encrypted: authorities can request the hosting companies to hand over your data. Secure email can be simplified by your group using only one email service such as riseup, tutanota, or protonmail. This means the “end to end” (from your email to your friends email) encryption is managed by the browsers and the email provider. The encryption only works if you use the same provider, meaning some or most people will need to create new email addresses.
Don’t use gmail and outlook
As well as your email, google gathers and stores a vast amount of personal information about you including your web searches. The less information you have stored with one company, the harder it is to build a profile on you. The same concept applies with Microsoft services such as outlook.com and hotmail.com
Full email encryption
To encrypt email across multiple email addresses and services will requires a tool called PGP and requires more complexity not covered here.