A popular pastime of observers of the government scene is to predict the imminent demise of the Postal Service. In fact, the last rites have been read over the mail system so often and so many obituaries readied that this dire fate has been accepted in some circles as conventional wisdom.

This is to serve notice to anyone who hasn't looked in his or her mailbox recently that the Postal Service not only lives and breathes these days, but also grows -- and adjusts to the times.

On the horizon, say the "experts," looms a growing tidal wave of electronic communications that will soon sweep the Postal Service, and others in the paper trade, completely away.

This ignores the fact that the electronics revolution has been going on in our country for decades. As early as 1923, the total of telephone calls in the nation began to exceed mail messages. Before that, it was the telegraph that threatened our future, and later it was radio, then television, facsimile, electronic fund transfer, etc. In the early 1970s it was widely believed that a main-stay item in the mailstream -- paper checks -- would all but disappear in a decade. Yet bankers now report that while electronic fund transfers have grown and will continue to grow, more checks are written today than ever before.

The continued growth of the postal system is not preordained, and advanced electronic communications will have a profound impact on our society. But I think the experts also miss some other points:

* Mail volume historically has followed the state of the economy. The only two times in the last 95 years that the volume has dipped significantly were during the Depression and during the recession of 1973-75. With new households proliferating (16.5 million since 1971) and real income expected to continue its growth despite inflation, conditions are favorable for further mail growth. The prospects will be enhanced if the Postal Service can keep to a stable rate policy, which I think it can.

* The "experts" have almost fully discounted any ability of the Postal Service to adjust to the times. Yet our pre-sort programs for mailers and our plans to automate mail processing demonstrate our ability to aid our own cause -- a fact supported by a 38 percent increase in productivity since the postal reorganization in 1970.

* Our Electronic Computer-Originated Mail (E-COM) service is due to begin this Monday. This service, which is for volume mailers who have computer capability, is an excellent example of how private-sector telecommunications technology can be wedded to the Postal Service's universal delivery system, to the benefit of all mail users. Basically, this system employs private telecommunications services to transport mail electronically, just as the Postal Service currently uses planes, trains and other means to move it physically.

With E-COM, volume mailers can electronically transmit computer-driven messages such as billing statements, marketing notices and announcements to a system of 25 "serving post offices" and be assured of delivery anywhere in the contiguous United States within two days. When the messages are received at these offices, they are automatically printed and enveloped, then delivered as first-class matter. The electronic transmission services will be provided by private common carriers.

We don't expect this system to make a major dent in conventional mail volume for a long while. But already, five common carriers have signed on to provide service, and others have applied to use the system through phone-line "dial-up" access. More than 100 organizations have applied to use the system to send portions of their mail.

The Postal Service and the mails are here to stay -- without infringing on any private-sector prerogatives. People will keep those cards and letters coming, although perhaps at a slower pace in the future. But just as television has failed to "kill" radio and newspapers, so the mail will go on in the grand electronic age.