Crossposted using Lemmit.

Original post from /r/techsupport by /u/Current-Ant-1274 on 2023-07-07 15:25:23+00:00.

Hey all,

A client of mine keeps trying to send email to my Gmail account but it always bounces back. This is new, we have emailed for months without this being an issue. He uses Hushmail and another email address. I’ve never marked him as spam, he’s in my contacts, not blocked, etc. I have been reading online and it appears to be an authentication issue on his end, but he doesn’t have issues with any other people he emails on gmail or other sites.

What can I do on my end to fix it? Is there something he needs to do? (Ideally it would be fixable on my end 😅)

550-5.7.26 This mail is unauthenticated, which poses a security risk to the 550-5.7.26 sender and Gmail users, and has been blocked. The sender must 550-5.7.26 authenticale with at least one of SPF or DKIM. For this message, 550-5.7.26 DKI checks did not pass and SPF check for [ sender email address | 550-5.7.26 did not pass with ip.