Mailboxes in 365 were not receiving email , this was caused by the recent Exchange 2010 security patches being installed – Update Rollup 32 for Exchange Server 2010 Service Pack 3 (KB5000978)

1. Get Exchange to the Latest CU

2. Windows Server 2008 SP2

   Ensure the latest Windows updates are applied, this must include:

   • KB4019276 to add TLS 1.2 capability as a default secure protocol for SChannel.
   • KB3161949 for the current version of WinHTTP.

   Install 3154517 for .NET Framework 3.5.1.

   Windows Server 2008 R2 SP1

   Ensure the latest Windows updates are applied, this must include:

   • KB3161949 for the current version of WinHTTP.
   • KB3080079 to add TLS 1.2 capability to RDS (optional).

   Install 3154517 for .NET Framework 3.5.1.

   Windows Server 2012

   Ensure the latest Windows updates are applied, this must include:

   • KB3161949 for the current version of WinHTTP.

   Install 3154517 for .NET Framework 3.5.1.

3)

When the above steps have been completed, registry settings need to be added to Enable TLS 1.2 for SChannel, and Enable TLS 1.2 for .NET 3.5.

TLS 1.2 for SChannel

Import the following:

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2]
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:00000001

.NET 3.5

Import the following:

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v2.0.50727]
"SystemDefaultTlsVersions"=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v2.0.50727]
"SystemDefaultTlsVersions"=dword:00000001