Sorry, no. Any service that will issue emails masquerading as 3rd-party domains, which does not use an effective authentication mechanism, is an open relay by definition.
I disagree. The “open” part implies there is no control at all on what email can be relayed. That is not at all the case here.
Spammers try their best to send spam through MailChannels all day long, through compromised WordPress sites, hacked user accounts, etc. We block 28% of all the messages that are submitted, and of what remains, only 2% is rejected by receivers.
That’s not at all what an open relay looks like. An open relay would accept 100% and likely be blocked within an hour across the internet.
