From examining mail server logs it looks like mailreport sends the email but it sets the from address in the header to <>. So a lot of systems will reject the email. Whereas pfSense actually puts the email in <email@domain.com>.
I set the from address in pfsense to the "Name <email@domain.com>" format. Then I first had pfSense sending an email and then mailreport sending a report. I sanitized emails and servers.
[07/Nov/2023 10:29:42] Recv: Queue-ID: 000010cf, Service: SMTP, From: <firewall@domain.net>, To: <email@domain.com>, Size: 637, Sender-Host: xxxx, Subject: pf.domain.net - Notification
[07/Nov/2023 10:29:44] Sent: Queue-ID: 000010cf, Recipient: <email@domain.com>, Result: relayed, Status: 2.0.0 , Remote-Host: aspmx.l.google.com
[07/Nov/2023 10:30:04] Recv: Queue-ID: 000010d0, Service: SMTP, From: <>, To: <email@domain.com>, Size: 7286, Sender-Host: xxxx, Subject: pf.domain.net Email Report: Test mailreport report, Msg-Id: <1234@pf.domain.net>
[07/Nov/2023 10:30:05] Sent: Queue-ID: 000010d0, Recipient: <email@domain.com>, Result: failed, Status: 5.3.2 550-5.7.1 Messages missing a valid address in From: header, or
[07/Nov/2023 10:30:05] 550-5.7.1 having no From: header, are not accepted. Please visit
[07/Nov/2023 10:30:05] 550-5.7.1 https://support.google.com/mail/?p=RfcMessageNonCompliant and review
[07/Nov/2023 10:30:05] 550 5.7.1 RFC 5322 specifications for more information. f13-20020a056e02168d00b0035905beb094si4928804ila.111 - gsmtp, Remote-Host: aspmx.l.google.com, Msg-Id: <1234@pf.domain.net>
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