SUMMARY I would very much welcome a lightweight option to send e-mail using the "legacy" way - only ask for recipient and then let it handle by mail command. Currently all e-mail binaries are thick clients with also the e-mail receiving capabilities. Access to e-mail via browser is quite common these days and big clients are becoming less relevant over time. Therefore having an option to configure send-only account via sendmail, postfix, msmtp etc would find its audience.
Perhaps adding a more generic approach would cover this. Currently there's a predefined list of mail programs. But what if one wants to implement his/her own logic? Ideally there's a [custom] script option exists which would only request for things like: recipient(s), subject, body, resolution and quality settings and it would execute a custom script passing all this options on standard input (e. g. as a JSON-formatted data). All the processing and error handling would then be a pure responsibility of the script.