This switch is located at Channel>Channel Settings>Ebay Settings.
If you enable this switch, the manufacturer part number (MPN) will not be sent to the channel. This is particularly useful if you have received MPN errors from eBay but don’t want to send the MPN to prevent data conflicts.
IMPORTANT NOTE: The Ebay item-specific MPN field will not be affected by this setting because it is directly populated from custom field mapping.