https://wordpress.org/support/topic/post2mail-broken-missing-argument-3-for-post2emailhelfpost2email_send

Hard to find a privacy friendly replacement. Most tools do other stuff.

• ask users for e-mail address and create a newsletter list. -> we want a simple redirection of Whonix blog posts to our existing Whonix mailing list, not start over collecting e-mail addresses
• newsletter list management by third party services such as mailchimp
• separate content newsletters, not blog post to mailing list forwarding
• contains an "unsubscribe" link, would not be useful to have a troll subscribe our blog post to mailing list mirrorer

No solution for this on the horizon.