To people mentioning public shaming. I had a mailing list with them removed with all contacts lost and account banned without even notifying me. Customer support indeed responded, but with something like your account was banned because you are involved into cryptocurrencies (i had hashcash.io - no selling or buying of crypto is even close) and we completely wiped all your data. Only after a hint about possible public…
How difficult was it to set up an SMTP server? I know that merely installing and configuring the software isn't that hard, but the common opinion of late seems to be that setting up things like MX records(I really don't even know how those work) is too onerous. If it's not that difficult, then there really should be fewer people/orgs relying on services like MailChimp.
As for sending out mail, one of the difficulties that MailChimp and similar services take care of is keeping the servers' IP addresses out of spam lists.