Why do email attachments still sync even though they have been disabled in settings?

Purpose

I have disabled Sync email attachments in the feature settings. Why do email attachments still sync? 

Answer

This is likely caused by the Email-to-Case Settings in Salesforce. If the Save email attachments as Salesforce Files option is enabled, attachments will still get synced because they are Salesforce files.

This occurs even if Sync email attachments is disabled in the Connector settings.

To prevent this from happening, you should also disable Save email attachments as Salesforce Files (uncheck it) in the Salesforce settings.

The following tables show what happens with various combinations of Salesforce and Connector settings.