Your recommendation please: big volume mail solution

[Arthur Sherman]

Hi,

A client asked me to build for him a mail solution, capable of sending up to
1 milllion emails a day, while each email doesn't exceed 50KB in size.

How do I calculate:
1) how many servers
2) how do I calculate the above
3) is there any max emails a day from IP/domain, which triggers black and
blocklists
4) what is your recommended software solution

On this stage, most distribution would be in single country.

Thanks in advance

Arthur