Why isn't Exchange accessible from my phone within the local network?

Question

Mail server

Hello. I’ll make a reservation right away, I don’t really understand Exchange, if the question is stupid - don’t hit me.
So. At the moment, the organization's mail is on Yandex. In the near future, we plan to move to our internal Exchange. But one thing is confusing - if an application on the phone (for example, Spark) hooks onto Exchange, then everything works fine from the outside, and if you connect to an access point inside the organization, then letters from this device do not leave, the mailbox is not updated. Is it possible to win somehow painlessly? Thank you in advance!

Answer 1

if the question is stupid - don't hit

The question is not stupid, but I will beat. :)
You need to start with diagnosing the problem.

emails from this device do not leave, the mailbox is not updated

This is a description of the symptoms at the user level, not the IT person. nslookup, ping, tracert, wireshark, that's it... (c) should be used for diagnostics.

I don't really understand Exchange

Diagnostics is needed to understand the main thing: it's not even about Exchange, but about the infrastructure of the local network (specifically DNS, routing, NAT).
Then there are two methods. 1) deal with internal DNS: https://www.google.com/search?q=split+horizon+dns
2) fence on the router is: https://www.google.com/search?q=hairpin+nat
Depending on [...] either any of the methods will help, or only one of them, or both together . It is impossible to say more precisely yet, local networks are different for everyone, there are also exotic configurations. If there is no exotic, then everything will work out for you.
PS Exchange at least fresh? Are all updates installed? And then over the past year, a fair share of Exchange servers (available on the Internet) have been hacked and continue to break. I'm surprised anyone else wants to use it.

Answer 2

You need to set up virtual directories, each has an InternalURL and ExternalURL property.
You explicitly have a domain configured in your organization, set up a DNS server so that InternalURLs are configured for access from the local network.