By default outlook can only send emails with max attachments of 20MB, and many mail servers allow attachments more than that, maybe more than 50 MB. Now if we upload file attachments in outlook windows more than 20MB then an error will appear "attachment size exceeds the allowable limit". So how to solve it. By setting the max attachment via the registry.
1. Press on the keyboard Windows + R
2. In the run dialog menu type regedit. and type OK.
3. Navigate to the menu as below
Outlook 2019 and 2016: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\\Preferences
Outlook 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\\Preferences
Outlook 2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\\Preferences
4. Double click pada MaximumAttachmentSize ,
If you don't find MaximumAttachmentSize add it manually add registry > Dword Value and fill the value with MaximumAttachmentSize then enter.
5. In the value data fill in the limit, for example we set 25MB then write 25600. If you have typed OK
