(NewsNation) — Some sanctuary cities are automatically rejecting emails that come from Immigration and Customs Enforcement, NewsNation has learned.

Acting ICE Director Patrick Lechleitner calls this a massive problem because the agency doesn’t just deal with deportation and immigration cases.

“There’s too many victims out there, and I don’t want to risk these victims and not support our state and local partners,” Lechleitner said in a recent interview. “(Homeland Security Investigations) is child exploitation investigations, human trafficking, so many crimes. Fentanyl, contraband investigations, narcotics more generally. … (We) can’t allow that political hot potato get in the way of that.”

To rectify this issue, Lechleitner says his agency is changing the address on some emails so they end with “DHS.gov” instead of “ICE.gov.”

What are sanctuary cities?

“Sanctuary cities,” or in some cases states, are places with policies that limit or deny local officials’ cooperation with federal immigration authorities. This can mean not providing information about someone’s immigration status or limiting the length of immigration detainers, according to the National Conference of State Legislatures, which notes that there is no legal definition for sanctuary cities.

Hundreds of communities, municipalities and counties across the U.S. consider themselves to have sanctuary policies, including New York City; Washington, D.C.; Newark, New Jersey; and Los Angeles. States with sanctuary policies include California, Illinois, Oregon and Washington.

Critics of sanctuary cities argue they undermine federal immigration law and make law enforcement agencies’ jobs harder. Proponents, meanwhile, say it is better to provide resources to migrants coming to the United States instead of detaining or deporting them.

While some have suggested sanctuary cities are less safe, studies by entities such as the Crime and Justice Research Alliance found there’s no evidence that they experienced higher crime rates or more violence.