If you are sending mail to a concentrated area, you may qualify for enhanced carrier route rates. You need at least 10 pieces per carrier route to qualify.

For Standard Mail, at least 200 pieces must achieve that 10-per-carrier-route concentration to qualify for enhanced carrier route rates--and you also have at least 200 pieces (or none at all) "left over" at regular Automation rates. (For more details, see the March 97 Mailroom Companion.)

For First-Class Mail, you can have as few as 10 pieces qualifying for enhanced carrier route rates, as long as you have at least 500 pieces total in the mailing. (For more details, see the March 97 Mailroom Companion.)

If you do a carrier route sort, Envelope Manager will determine if your mailing qualifies. Since Enhanced Carrier Route rates are cheaper, you should turn on Use ECR Automation as a general rule.