Of all the topics of international affairs that might prompt people to write to the U.S. State Department, the one that brought in the most mail this year was an obscure religious community in the jungles of Northern Guyana.

That community, which emerged from its obscurity with brutal suddenness last weekend, was the American settlement known as "Jonestown," founded four years ago by the Rev. Jim Jones and members of his Peoples Temple church.

Between January and August this year, the department said, it received more than 1,200 letters about the Guyana colony. More than 60 percent, mostly form letters suggestive of a mass-mail campaign, praised the settlement and Jones; the remainder, which also ran heavily to form letters, charged that Jonestown's residents were being held against their will and tortured by armed guards.

The flood of mail to the secretary of state, supplemented by scores of inquiries from members of Congress and other officials who had received mail about Jonestown, almost surely will be cited in the months to come as public and private organizations look into one of the mysteries of the mass murder-suicide at Jonestown last weekend: why the U.S. Embassy in Georgetown, Guyana, was unaware of the bizarre practices that were reportedly common at the settlement.

State Department officials, under lengthy questioning from reporters, have defended the embassy's action, reviewing in detail its efforts to learn the truth about the colony.

For the moment, however, the department is concentrating on the aftermath of the tragedy. A special operations center, staffed by consular officers round the clock, has been established to deal with public inquiries and coordinate the work of military personnel at the site of the massacre.

The military is employing techniques developed during the war in Vietnam for handling jungle massacres. An Army graves identification unit is at Jonestown to try to identify the bodies. The dead will be ferried on four specially equipped Air Force transports to a huge mortuary at Dover Air Force Base in Delaware that was built to accommodate Vietnam casualties.

The first plane was scheduled to leave Georgetown, Guyana, at 10 p.m. EST yesterday and to arrive in Dover at 6 a.m. today.

State Department officials reported great difficulty locating next-of-kin of the victims of the Jonestown carnage, since most of the dead had none of the standard identification documents that might lead to relatives. They said the federal Privacy Act prohibits a general release of the names of the dead, which might prompt relatives to contact the department.

A California television station Tuesday night read an "unofficial" list of the names of the dead, prompting an explosion of calls to the State Department early yesterday. The department would not verify any of the names on the list.

A smaller mystery about Jonestown cropped up Monday when the Guyanese Embassy released a list of 39 Americans who it said had written character references for Jones when he asked permission to start his colony. Most of those on the list said they had no record or recollection of such correspondence.

The embassy said yesterday that Jones had provided letters from five of the 39. The remaining "reference" were cited on a list Jones gave the Guyanese government.

In reviewing its reaction to complaints about the Peoples Temple settlement, the State Department said that officers from the embassy in Guyana had interviewed about 75 Jonestown residents to ask about charges of abuse.

Many were questioned privately in an open field with no other members of the cult present, the department said. But none of those questioned provided any evidence of abuses, the department's spokesmen said.