In Microsoft Exchange Server 2019 or Exchange Server 2016, EdgeTransport.exe crashes because of a stack overflow exception. You may see this event in the application logs:
Log Name: ApplicationSource: Application ErrorDate: DateTimeEvent ID: 1000Task Category: (100)Level: ErrorKeywords: ClassicUser: N/AComputer: ComputerNameDescription:Faulting application name: edgetransport.exe, version: 15.1.1847.3, time stamp: 0x5d5c6650Faulting module name: clr.dll, version: 4.7.3062.0, time stamp: 0x5ab9567cException code: 0xc00000fdFault offset: 0x0000000000004fb4Faulting process id: 0xfcFaulting application start time: 0x01d59a7080bdc2fdFaulting application path: C:\Program Files\Microsoft\Exchange Server\V15\Bin\edgetransport.exeFaulting module path: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\clr.dllReport Id: ReportIDFaulting package full name:Faulting package-relative application ID:
This issue occurs because the error "451 4.7.0 Temporary server error. Please try again later. PRX5" is populated in the smtp.target response variable. It causes the stack for filling the InboundProxyLayer's buffer keeps building up.
To fix this issue, install one of the following updates:
For Exchange Server 2019, install the Cumulative Update 7 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.For Exchange Server 2016, install the Cumulative Update 18 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.