not as it currently stands – if I understand the dilemma… 

we solely use WP to send the email…  for simple press to turn and send the email, we would have to implement some sort of php mailer class…  out of scope for us really… 

Since I know nothing about this postmark api, I guess its possible it could simply the sending of emails compared to an entire mailer class… but it would still require from scratch new code, probably in form of sp plugin…  but dont know enough about postmark to even hazard a guess if possible or how difficult…

does the postmark plugin have an api?  that is hooks and filters that you could use to override the default behavour?