IIRC I got a bounce, went to investigate, and found that Caprica had been blacklisted.
This is the mail system at host soproxy7.mail.unifiedlayer.com.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<xxxx@gmail.com>: host gmail-smtp-in.l.google.com[x.x.x.x] said:
550-5.7.26 This message does not pass authentication checks (SPF and DKIM
both 550-5.7.26 do not pass). SPF check for [xxx.net] does not pass
with ip: 550-5.7.26 [x.x.x.x].To best protect our users from spam,
the message has 550-5.7.26 been blocked. Please visit 550-5.7.26
https://support.google.com/mail/answer/81126#authentication for more 550
5.7.26 information. h9-20020a92c269000000b002e45aa5c425si10677861ild.89 -
gsmtp (in reply to end of DATA command)
Reporting-MTA: dns; soproxy7.mail.unifiedlayer.com
X-Postfix-Queue-ID: 394078077BAA
X-Postfix-Sender: rfc822;xxx@xxx
Arrival-Date: Wed, 17 Aug 2022 13:28:15 +0000 (UTC)
Final-Recipient: rfc822; XXX
@gmail.com
Original-Recipient:
rfc822;xxx@gmail.com
Action: failed
Status: 5.7.26
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.26 This message does not pass authentication
checks (SPF and DKIM both 550-5.7.26 do not pass). SPF check for
[%%%%.%%%] does not pass with ip: 550-5.7.26 [7x.x.x.x].To best
protect our users from spam, the message has 550-5.7.26 been blocked.
Please visit 550-5.7.26
https://support.google.com/mail/answer/81126#authentication for more 550
5.7.26 information. h9-20020a92c269000000b002e45aa5c425si10677861ild.89 -
gsmtp