We are primarily a web design and web development (Australian-based) agency. We currently have a great server manager who we want to stick with for all our web hosting. We have around 400 client accounts.
However, our server manager is not keen to run email systems for us. So we are looking for alternative email infrastructure for at least 100 clients (all on their own custom domains) and possibly up to 500, with up to 2,000 individual email accounts.
Around 10% of our clients are running Google G-Suite or Office365 but many don't want to pay extra for this. We're happy to pay a biggish monthly cost but we don't want to pay a huge amount per domain or the costs will be too high.
We are slowly moving a lot of our clients to alternative outgoing systems such as AmazonSES and the awesome PostMark, but it feels like a point-in-time where we need to look for an alternative email infrastructure to offer as resellers, for both incoming and outgoing.
We want to manage the email accounts via a simple system (something like the mail system on cPanel) but we don't really know what's out there, or the right questions to ask. Hence this annoyingly-amorphous question!
So, can anyone please point me in the right direction for who to use, but perhaps more importantly for what to ask for when looking to be email server managers ourselves to some extent?
We would prefer to use Australian servers.