It appears we started receiving errors similar to the one below since last week on our Exchange Server 2016. A staff member stated he was receiving emails normally on his PC but not on his phone.
This server has been set up since November 2019 without any issues. The default ports in the firewall were added as part of the Exchange installation.
I have seen information online that suggest doing a variety of things such as creating registry keys, change the page file to installed memory and a number of other steps indicated here: https://docs.microsoft.com/en-us/archive/blogs/david231/for-exchange-2010-and-2013-do-this-before-calling-microsoft
Are all of these steps really required to resolve the issue? The KB905013 does not appear available after doing an online search
I see https://social.technet.microsoft.com/wiki/contents/articles/35919.event-id-1040-on-exchange-servers.aspx about changing the heartbeat interval value in the web.config file but should this really be necessary if there hasn’t been an issue before now? Is modifying this file recommended?
Log Name: Application
Source: MSExchange ActiveSync
Date: 9/22/2020 11:45:51 AM
Event ID: 1040
Task Category: Requests
The average of the most recent heartbeat intervals  for request [Ping] used by clients is less than or equal to .
Make sure that your firewall configuration is set to work correctly with Exchange ActiveSync and direct push technology. Specifically, make sure that your firewall is configured so that requests to Exchange ActiveSync do not expire before they have the opportunity to be processed.
For more information about how to configure firewall settings when using Exchange ActiveSync, see Microsoft Knowledge Base article 905013, "Enterprise Firewall Configuration for Exchange ActiveSync Direct Push Technology" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=905013).