https://www.dhs.gov/govdelivery-privacy-policy-and-notice
https://www.ftc.gov/system/files/attachments/privacy-impact-assessments/govdelivery_7-10-19_pia_no_sig.pdf
FWIW, here are the DHS and FTC saying that they use GovDelivery - with the FTC's report there mentioning that it's provided by Granicus, which is what govdelivery.com redirected to for me.
Now, at most I'd only say that confirms it's a legit site that the government really does use. Not necessarily that some other party couldn't be using it for more nefarious purposes.
https://i.imgur.com/qUAL3fG.gifv