How to transfer mail to the internal server of the organization?

Question

Email

Good day.
Help a novice sysadmin, but an experienced enikey.
There is a small company: 5-6 workstations on Win10, one Windows Server 2016 server. The server is currently used as a file cleaner. All computers are in a workgroup, not a domain.
The company has a website, i.e. like a branded domain. Mail works through Yandex. As I understand it, he is delegated the management of domain mail.
It is necessary to configure the work of mail on the internal server. It is necessary that within the company the exchange of mail went through it. At the same time, to be able to exchange mail with the outside world.
Questions:
1. Whether it is necessary to do all computers in the domain?
2. Should the server have a white ip?
3. Do you need any additional services from a hosting provider?
4. I plan to implement it all through Exchange. Is this the correct solution in this case?
Thanks in advance.

Answer 1

1. No
2. Not required, but highly desirable.
3. A-record in DNS, PTR-record at the provider.
4. If the organization has extra money.

Answer 2

Lots of words and extra tags .
In MS Outlook, configure the connection (main) to MS Exchange. And additionally any external mailboxes with storage in MS Exchange.

Answer 3

1. Not necessarily. A domain is, of course, not only valuable fur , a single point of control, politics, a silent installation, and so on - but also a decent amount of money (You don’t think to install a pirate, right?)
2. If there is none, it is required. If you already have at least one - pulling out the bare #opy Windows is an extremely risky undertaking
3. The provider may need to change the PTR record. From hosting - changing A-records, MX-records, if you do not maintain DNS yourself
4. No, but if there is a decent amount of extra money - M$ will only be delighted with a gift