Hi,
I tried to sign up for this forum which needs me to click a link in an confirmation email sent to me.
However, that mail never reached me.
As I run my own mailserver the postfix logs told me why:
Jun 4 14:03:10 mail postfix/smtpd[27647]: warning: hostname mx-out-01a.sjc3.discourse.org does not resolve to address 72.52.80.54: Temporary failure in name resolution
Jun 4 14:03:10 mail postfix/smtpd[27647]: connect from unknown[72.52.80.54]
Jun 4 14:03:11 mail postfix/smtpd[27647]: NOQUEUE: reject: RCPT from unknown[72.52.80.54]: 450 4.7.25 Client host rejected: cannot find your hostname, [72.52.80.54]; from=<cosmos1+verp-585d7[censoredforprivacy]@discoursemail.com> to=my-address-for-cosmos@my-address-for-cosmos-mailserver.com proto=ESMTP helo=<mx-out-01a.sjc3.discourse.cloud>
My mailserver is configured to
reject_invalid_helo_hostname
reject_non_fqdn_helo_hostname
reject_unknown_client_hostname
The only chance to receive that confirmation mail was to temporarely deactivate the option(s) above.
As every good mailserver should have those options turned on I suggest changing something on the sender side. Maybe a lot of people can not sign up here because of that.