On Christmas Eve, United Methodist minister Dan Louis received a haunting message that threatened to change his world.

But the message wasn't from on high. It was from the U.S. Postal Service.

The message said that the newspaper Louis edits, the United Methodist Reporter, would have to find nearly $1 million to offset new higher postage costs scheduled to go into effect this Sunday for nonprofit organizations and other preferred mailers. The increases were ordered as part of the Reagan administration budget cuts.

"If God wants there to be a publication of this nature in His kingdom, there will be," said Louis, adding that he was devastated by the news of the rate changes. "It literally got to the point where we were looking at nickels and dimes so we wouldn't have to pass this increase onto the backs of our churches," he said.

About 200,000 nonprofit organizations across the country that depend on low-rate postage on mailings to inform constituents or raise contributions will be hit hard by the new costs, according to nonprofit mailing associations.

Such groups had enjoyed preferential mailing rates for years because Congress considered their newsletters, fund-raising envelopes and newspapers important to the public good. But last month Congress lifted the subsidy from groups ranging from veterans and farm organizations to arts associations and the March of Dimes, forcing the Postal Service to raise its rates.

Critics have said for years that it was unfair for taxpayers and other Postal Service users to subsidize the nonprofit groups' mailings.

But some mailing groups predicted job losses within nonprofit organizations, doubling of subscription rates for their publications, closing of some newsletters and a domino effect on the social services and public health research that such groups support.

"It's kind of like a tornado, I guess," said Don McGregor, editor of the Baptist Record in Jackson, Miss.

"I literally, as well as figuratively, wept," said Alan Caplan, circulation and marketing director of the Jewish Exponent, a newspaper whose income helps support 50 programs of the Federation of Jewish Agencies of Philadelphia, the paper's owner. The programs range from services for the aged and orphaned to help for Jewish emigres from the Soviet Union. "I was absolutely floored."

Not only will religious publications be hurt, but activities of research foundations, such as the March of Dimes and the American Lung Association, which depend on their nonprofit mailing status to solicit the contributions that make up as much as 85 percent of their funding.

"We mail more than 100 million pieces of mail a year in fund-raising," said Clyde Shorey, a March of Dimes vice president. "It's going to cost more than $2 million a year" in additional postage costs, Shorey said. "We'll have $2 million less to put into services."

About $51 million of the American Lung Association's $60.5 million in annual revenues came from direct-mail contributions, said Bob Weymueller, director of government relations for the lung association. That group's $3.5 million annual postage costs will increase by about $2.3 million this year, Weymueller said.

"We have to make up for it somewhere," Weymueller said. "It just means there's less in the way of anti-smoking programs and pediatric self-help programs" for youngsters with chronic diseases. Most of the group's money comes from "lots of contributions from lots of people rather than major gifts," so mailing must be cut back carefully, Weymueller said.

What particularly galls Weymueller, he said, is that the postage increases "came at a time particularly when the government says it is trying to encourage volunteer work."

As part of the Postal Reorganization Act of 1970, Congress decided that subsidies for mail would be phased out by 1987. But last year Congress cut the Postal Service's fiscal 1982 subsidy for nonprofit and other preferred mailers from $800 million to $614 million.

Congress also ordered the Postal Service to adjust preferred mail rates this year, instead of through 1987, to make up for the lost funds, a Postal Service spokesman said.

The $614 million will be used for overhead and for two preferred groups whose subsidies Congress ordered the Postal Service to cut less severely. They are senders of second class mail within a county, mostly small newspapers, and fourth class library mailers, the spokesman said.

Subsidies were eliminated for third class nonprofit bulk and several second class nonprofit, classroom and state agricultural categories. The rates, however, still are lower for these mailers than for businesses making comparable mailings, the spokesman said.

Although the rates vary by class of mail and whether they are sorted by destination before mailing, the new non-subsidized rates will range from 20 to 400 percent higher.

The nonprofit groups said they probably will increase subscription rates, try to absorb some of the increases, cut back in other areas or even deliver some newsletters by hand. As a last resort, staffs will be laid off and some operations halted.

For example, Consumers Union, publisher of Consumer Reports, recently said the sagging economy and a $2 million postal rate increase forced it to lay off more than 30 of its 230 employes, to close three advocacy offices and to trim the size of its magazine, which accepts no advertising.

Because the Postal Service was ordered by Congress to increase rates, no hearings were held on the changes, Postal Service spokesmen said.

"There was no time to fight it or put up our defenses," the Jewish Exponent's Caplan said. "It was a crushing, crushing defeat for us."

The National Association of Black Manufacturers said it has attempted to be self-sufficient, relying on contributions rather than federal funds. But the postage increases for its four publications "will affect the association as far as the cash flow," said Eugene Baker, association president.

Local arts groups were hurt first by a reduction in the National Endowment for the Arts, and now they are faced with the postage increases, which threaten their private contributions, mailings of performance announcements and, consequently, a possible reduction in program attendance, said Craig Hosmer, assistant manager of the Washington Performing Arts Society, which mails as many as 300,000 letters at one time.

"You fall back on things that you did in your younger days," Hosmer said. "It's exhausting. You set up booths and sell directly at concerts, give away a free record album if we can get them donated.

"We're not as quick to take risks with unknown artists," Hosmer continued. "We will reevaluate what we bring to the Kennedy Center."

Of the society's annual $2.5 million budget, $15,000 last year went to postage, but "we can't afford to have double" spent on postage this year, he said. "Our budget is set for the year."