Create Templates from existing emails

Can you please implemant the function like templates in Postbox. For me it's necessary, that I can make E-Mails mostly complete ready for sending. So I can make it complete, with all E-Mail Adresses I sent to and need in case of using the templates only send, without spending time for creating all recipient I need for these Mails. I wonder why this is not possible with the EM-client. This was a standing procedure by all other I had before.