Why did Blackberry services use special mobile internet settings?

Question

blackberry

Why did blackberry services require separate mobile Internet settings (APN blackberry.net, for example), and therefore special support from the mobile operator, while smartphones from other manufacturers (Android, iOS) managed with the usual settings?
It seems to me that the trick there was in instant message delivery, and on a regular mobile Internet under NAT, incoming connections are closed, and keeping a session behind NAT is expensive, polling the server is not so fast. Therefore, on a separate APN there could be a special server that has direct access to the internal IP addresses of phones, without any NATs and the possibility of incoming connections. A message came, the server sent it directly to the IP of the phone. And mobile IPv6 had not yet received distribution.
And Android and iOS appeared later, when the networks and capabilities of mobile devices were more developed, and the requirement for prompt delivery was not so obvious (even now, mobile notifications often arrive with a delay), and therefore a regular session was enough due to NATa, especially since this easier and no special support from the operator is needed for this.

How was it actually set up?

Answer 1

The trick was that Blackberry needed access to their equipment installed by telecom operators, and the rest needed simple access to the Internet.

Answer 2

In Blackberry, the Internet worked with the help of the so-called Blackberry Internet Services (BIS) . In fact, access was organized through a special SSL tunnel from the phone to the BIS server, within which all data was transmitted (which was described in the playbooks), but the BIS server had to be separated from ordinary subscribers.
And taking into account the requirements of our legislation (a ban on the import of uncertified crypto-means as communication equipment - you won’t get a certificate of conformity for a handset, you won’t be able to sell it in stores, for example , the approach is the same with phones), the server had to be at the operators.