Change the limit for the number of MIME body parts
Supported on: At least Windows Server 2008 R2 or Windows 7
Registry
HKCU
software\policies\microsoft\office\16.0\outlook\options\mail Options
mimebodies decimal
- range ?-99999 Description
By default, the limit is 250 for the number of MIME body parts when an e-mail message is converted from MIME to MAPI. The number can be set to any positive integer. This helps prevent scenarios in which Outlook hangs while attempting conversion.