Matt,
Thanks, but I don't feel like managing a huge list of ips for a single customer, they list a bunch of /20's, /24's, et al, on the support page, it's like basically saying spf to +all. Honestly, we can probably do everything that AppRiver can do already, so I'm going to try and have them just go direct to us.
Scratch the ARC deal as well, I just tested this out, and you guys are accepting the emails fine. Gmail is doing a SRS rewrite and resigning with ARC. I just did a forward from GMail to my personal and it's fine.
[2020.04.22] 13:18:29.526 [49227] Spam check args: from: eric@securedomain.com; messageID: 49227; messagePath: M:\SmarterMail\Spool\SubSpool1\191349227.eml; sender: gmail.username+caf_=local.username=domain.com@gmail.com; sendersDomain: gmail.com; sendersIp: 209.85.222.50; returnPath: gmail.username+caf_=local.username=domain.com@gmail.com
[2020.04.22] 13:18:29.526 [49227] [209.85.222.50] Valid reverse DNS entry found: mail-ua1-f50.google.com
[2020.04.22] 13:18:29.588 [49227] Running SPF check
[2020.04.22] 13:18:29.588 [49227] Finished SPF check; result = Pass
[2020.04.22] 13:18:29.588 [49227] [DKIM] Performing DKIM check...
[2020.04.22] 13:18:29.588 [49227] [DKIM] Result: Good.
[2020.04.22] 13:18:30.447 [49227] Spam Checks completed.
[2020.04.22] 13:18:30.447 [49227] SpamCheck Processing Thread Completed