My question is strictly related to transactional emails and common best practices like using different email providers for transactional and marketing emails, relevant Subject, From and Reply-To addresses, etc. is assumed.
Would using multiple transactional email providers with a different affinity to the destination domain or even full email address increase my deliverability?
e.g. using let's say mandrill to send to gmail and postmark for everything else or even mandrill for user1@gmail.com and postmark for user2@gmail.com
Is it worth splitting transactional emails in first class ones (reset password, verify email, etc) and second class ones (merely informative) and using different email providers for each?
e.g. using mandrill for password reset and postmark for the welcome (registration successful) email
What else is advisable?