And the reason that MailChimp's servers are trusted for delivery to third parties is that they do front-end filtering to keep spammers and scammers off the platform so that third party mail recipients have a reasonable expectation that they can rely upon MailChimp's due diligence legwork. In this case MailChimp is deciding that the vast majority of ICO and Blockchain marketing is spam/scam email and continuing to allow it has a negative impact on those high delivery rates.

Anyone with an email server can try, but given the nature of this particular community it is more likely that this competitor would soon find their email delivery rates hitting 0%.