There is no global change for this.
Go to your "Options" Tab > "Global" and make sure "Warn if a record was changed but not saved" is checked.

Now open edit vendor maintenance, start with the first vendor. Get on the "Purchase Info" Tab, check the box for email then go to the top of the page and click the forward arrow beside the vendor name above to advance to the next record. A pop up screen will come up and ask you to save. Click yes and continue this pattern.