Hours after The Post revealed newly obtained emails that show how cozy Mayor Bill de Blasio once was with a crooked campaign fundraiser, City Hall said it’s revamping the policy for saving such correspondence.

“We’re developing one,” mayoral press secretary Eric Phillips said Tuesday. “One didn’t exist in any meaningful way, as we’ve said.”

Last month, federal prosecutors at an NYPD corruption trial unveiled emails between de Blasio and developer Jona Rechnitz that had not been released by City Hall in response to a 2016 Freedom of Information request from The Post.

In response, a de Blasio spokeswoman said City Hall employees “are under no requirement to retain every e-mail ever written or received,” citing a policy developed by de Blasio’s predecessor, Michael Bloomberg.

FOIL expert Robert Freeman, executive director of the state Committee on Open Government, said any ­emails written by a government official should be kept if they “relate to the performance of one’s duties.

“We’ve all seen the portion of the communications . . . and it’s clear they relate to [de Blasio’s] capacity as mayor.”