Text-only format for outbound SMTP messages

Context:
-> We are trying to implement a PGP-encrypted mail flow where Chatwoot is playing the role of the outbound SMTP client.
-> The latter is sending HTML formatted message to our Exchange Server which then is attempting to send to a PGP universal server.

Problem:
-> Chatwoot is sending HTML only formatted messages.
-> PGP universal is expecting Text-only format

As per this part , we are seeing that the format is always HTML:

def send_mail_with_liquid(*args)
mail(*args) do |format|
explored sending a multipart email containing both text type and html

parsing the html with nokogiri will remove the links as well

might also remove tags like b,li etc. so lets rethink about this later

format.text { Nokogiri::HTML(render(layout: false)).text }

format.html { render }
end

Is there an option to send text-only messages ? If not, can you please consider that feature?