Okay. So if I understand your reply correctly, seeing potomac1050.mktomail.com listed as a spammer could be due to something we did or it could be the result of other emails coming from a shared IP - there's no way to know for sure. Is that right?
Now you've lost me. I saw it listed in some email suspend causes.
On Tue, Jun 4, 2019 at 9:53 AM Sanford Whiteman <firstname.lastname@example.org>
Now you've lost me. I saw it listed in some email suspend causes
Oh, it can be listed, sure. But what you're posting here about Gmail is orthogonal to that.
Dedicated IP is possible, we use it as my firm requires it...but I agree it is not common and most use Marketo's shared IPs.
Yes, it has to be this way because no service can allocate a public IP to every individual tenant. There simply aren't enough IPv4 IPs to go around in the world, let alone in a single company's hands.
I agree with Sandy's response but just in case, if you haven't yet, check whether SPF has been configured correctly - I've seen this issue when authentication has not been set up.
But SPF isn't correct when it includes machines that actually shouldn't be allowed to send mail using your domain as the envelope sender.
Blindly including mktomail.com in SPF for shared instances is a security risk (however mild) b/c it needlessly allows people to impersonate your domain. But the far bigger risk is you break your SPF entirely by going over DNS lookup limits. In fact Denise's client's domain has used all 10 of their allowed DNS lookups because they included Marketo unnecessarily! If they tried to include one more domain, the whole thing will break -- they will not in effect not have an SPF record.