- Press Windows-R
- Type “regedit” in the Run dialog
- Click OK
- Find proper key for you outlook version
-
2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Preferences 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Preferences 2016: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences
- If you see MaximumAttachmentSize double-click it, if not create it as DWORD
- Enter the desired attachment size limit in KB under Value Data: (for 25 MB limit use “25600”)
- The default value (with MaximumAttachmentSize not present) is 20 MB or “20480”.