PGP lets you do two common things with email: encrypt it or sign it (or both).
To keep email private, encrypt it.
To let your recipients verify the message is from you and the content did not change, you should add a signature like this:
Recipients who use PGP will be able to verify this signature. Any decent PGP software will do.
In FlowCrypt, it will look like this:
The recipient will see a green (or red) signature in the corner. Green means that the content matches the signature (therefore was not tampered with).
Currently you can either encrypt an email or sign it, not both. Both encrypting and signing the same email will be possible soon. Also, for now, only the content of the email gets signed - attachments won't. This is all planned.
Try it out & let me know what you think!