How do I send an encrypted message to someone who doesn't have the kodamail extension?

This can be done using AES 256 encryption, you just have to figure out a secure way
to get the pass phrase to them so they can decrypt it.

There are two options available to decrypt the message:
1. When you create a passphrase for AES 256, you can tick the box to have a link inserted at the bottom of the email, then all the receiver has to do is click the link in the email and enter a pass phrase.
2. Tell the receiver to (right click) copy the message and paste it into the box at: https://kodamail.com/symmetric/decryption/ and enter the pass phrase.
As not everyone is familiar with copying and pasteing, option 1 might be used.