Lamson isn't an open source alternative to mailgun and sendgrid per se, it's an open source alternative to writing your own library for email.
With that said, specific functionality is more a question of learning lamson, and tying in libraries that do do what you want, or finding someone that already has on Github.
For your use case, you would be tying together and implementing bits and pieces of this yourself. Part of the reason for Lamson existing is to enable programmers to solve their own problems with a common sensical base to work off of.
It's more of an equivalent to a web framework than a CMS.
If that isn't workable, you'll have to either hire somebody familiar with Lamson to hack it up for you, or you'll be at the mercy of existing plugins to tie an MTA into MongoDB. (Doesn't exist).
Do you have a more specific question for me to address? The answer to pretty much everything you brought up is "Cool, so go make it". The point of Lamson being the way it is, is so that you're not limited by the creator's intentions, just by your programming ability.
With that said, specific functionality is more a question of learning lamson, and tying in libraries that do do what you want, or finding someone that already has on Github.
For your use case, you would be tying together and implementing bits and pieces of this yourself. Part of the reason for Lamson existing is to enable programmers to solve their own problems with a common sensical base to work off of.
It's more of an equivalent to a web framework than a CMS.
If that isn't workable, you'll have to either hire somebody familiar with Lamson to hack it up for you, or you'll be at the mercy of existing plugins to tie an MTA into MongoDB. (Doesn't exist).
Do you have a more specific question for me to address? The answer to pretty much everything you brought up is "Cool, so go make it". The point of Lamson being the way it is, is so that you're not limited by the creator's intentions, just by your programming ability.