On a Plesk for Windows server, MailEnable webmail shows 503 Service Unavailable.
- The IIS application pool MailEnableAppPool crashes on the attempt to access webmail.example.com.
Event Viewer shows events with ID 2280 and 5139 five times in a row. After that, the Event with ID 5002 appears and the application pool is stopped:
Event ID 2280:
PLESK_INFO: The Module DLL C:WindowsSystem32inetsrvModSecurityIIS.dll failed to load. The data is the error.
Event ID 5139:
PLESK_INFO: A listener channel for protocol ‘http’ in worker process ‘12864’ serving application pool ‘MailEnableAppPool’ reported a listener channel failure. The data field contains the error number.
Event ID 5002:
PLESK_INFO: Application pool ‘MailEnableAppPool’ is being automatically disabled due to a series of failures in the process(es) serving that application pool.
Switching the option Enable 32-Bit Applications to True value in Start > Server Manager > Tools > Internet Information Services (IIS) Manager > Application Pools > MailEnableAppPool > Advanced Settings works around the issue:
The module ModSecurityIIS.dll cannot be loaded due to missing several Microsoft Visual C++ Redistributables with x64 architecture.
Connect to the server using RDP.
Install all the packages
vcredistXXX_x64.msifrom the folder
Note: Replace 17.5.3 with the version of Plesk installed on the server.
Open the IIS Manager in Start > Server Manager > Tools > Internet Information Services (IIS) Manager and restart the application pool
MailEnableAppPoolin server_hostname > Application Pools > MailEnableAppPool > Stop/Start: