From my research, this statement is true.
From the American Federation of Government Employees, of AFGE, website (which is linked below), as of October 3rd, 2025, the AFGE did in fact file a lawsuit against the Trump Administration, specifically the Department of Education, for sending out emails with automatically added partisan language without the consent of the workers. The AFGE president, Everrett Kelly states that this action "blatantly violates the law in yet-another assault on federal workers' rights". The AFGE states that the unknowing addition of partisan language into emails violates the workers' First Amendment Rights, impeding on their freedom of speech and belief. For this claim, this primary source is unbiased when it comes to answering if this lawsuit is actually happening, though still in favor of federal workers' as it is the official federation of government employees. While looking through this source, I also found the official complaint file (also linked down below) of this lawsuit. The first sentence of the complaint that states why this complaint is made, "To blame its political opponents for the federal government shutdown that began on October 1, 2025, the Trump Administration has gone to extraordinary measures to leverage its control of federal agencies", immediately backs up the claim that this is against the First Amendment Rights of workers if it is true the Trump Administration is tying beliefs to non-consenting individuals for leverage.
While these sources may be biased toward the AFGE as they come from the official website like I stated before, when it comes to if this claim that a lawsuit was filed is true or false, these websites are not biased and state that this is true. The reasoning will be biased in favor of the workers' affected but overall, the fact that a lawsuit is presented is confirmed
Here is the AFGE statement:
AFGE | Trump-Vance Administration’s Use of Employees’ Emails to Send Partisan Political Messages Challenged by Largest Federal Worker Union
Here is the case file:
Microsoft Word - Shutdown OOO complaint