How send encrypted email only

how do i send encrypted email?
version 5.600 & 5.733 says:
encryption not possible. some of the selected receiptients dont support this feature

Get them to use clients that support it then I guess - you or your K-9 can’t change it if they can’t receive encrypted emails.

do you mean k9 will determine recipient supports encryption as soon as i type senders email id?

K9 probably “knows” which providers support it, I don’t know.