We feel fortunate that the Postal Service has been the subject of Herblock's editorial humor over the years.

However, in his June 6 cartoon Herblock, by innuendo, misinforms the American public, which uses the mail, and does a disservice to the Postal Service, which processes and delivers it.

The reason first-class letter mail costs more than what Herblock terms "junk mail" -- we call it bulk business mail -- is that it gets higher priority treatment and requires more handling. That's just the opposite of the message conveyed in the cartoon.

The U.S. Postal Service's mission is to break even financially -- not to make money. By law each class of mail must pay its own way without tax subsidies. Since bulk business mailers are required to presort their mail, it costs us less to handle it. That's why that mail goes for a lower rate, not because we are buttering up one segment of the mailing public at the expense of the others.

I certainly would never tolerate the holding back or slowing down of first-class mail to accommodate any other phase of the service.

As for congressional mail, that is a matter determined by Congress alone.

This is Herblock's fourth recent postal bash. I hope my effort at setting the record straight will redirect his powerful pen into other areas warranting his attention.

ANTHONY M. FRANK

Postmaster General

Washington