This article reads like a product brief and skims over several important aspects very lightly.

TL;DR of this comment: Mass email is almost a lost cause, and even MailChimp cannot really help everyone because of the players in email platforms.

I have a very limited experience where I tried MailChimp for a small set of committed people (about 100) who had voluntarily given their email addresses for receiving notifications for a specific purpose. It didn't really work for the first (and important) email and we had to resort to just mailing people in BCC and hoping they'd receive it. The content was also reviewed a few times to make sure it didn't look like a spammy email.

There were multiple problems, and I didn't know (and there was no way to know) if the problems were on MailChimp's side or Gmail or both. Worse, there is no way to help oneself in such situations to increase the email delivery rate.

1. On follow up, several recipients said that they didn't even receive the mail. It wasn't in the spam folder or the "Promotions" folder of Gmail either. MailChimp's statistics didn't indicate any delivery issues or that it wouldn't deliver them (am not referring to the mail opening click tracking/beacon tracking). It showed all of them as sent.

2. Gmail by default seems to classify emails as promotions when they come from Mailchimp or other providers. This means, for all practical purposes, the emails are invisible to people using the web interface. People aren't used to checking anything other than the inbox there and ignore that increasing count of unread mails in promotions.

3. For most people who now check emails on mobile devices, they do not look at the spam folder at all. With every person having multiple email addresses, they seem to have a list of inboxes they look through and act. All the other folders in every mailbox are ignored. So any email that goes into spam is more likely to be missed, and later gone forever after the limited retention period of the providers.

4. Though email is the only (?) federated, widely and easily available communication platform, providers like Gmail have cornered the market and dictate with a very heavy hand what ought to be delivered and what oughtn't. At least in my case, I may have had better luck using Google Groups instead of trying MailChimp just for the templates, personalization and all the nice features that can never trump emails being delivered to the recipients. But even that may not have worked.

5. In my observation, Gmail doesn't trust users sending mails to multiple people and likely doesn't deliver mails or puts them in the spam folders. I can't imagine that at its scale, Google seems incompetent in differentiating one person, using Gmail from a specific location boundary (IP address range, browser, OS) for quite sometime who wants to send a mail to several people, from spammers and bots. It ends up punishing everybody.

To MailChimp's credit, the free tier is generous for people with very low to moderate frequency and subscriber needs. MailChimp's website has a lot of useful information on email campaigns.

Overall, mass email of any kind is fraught with more problems in getting the message to others than other media like the walled garden variety of chat and social media platforms. I wouldn't rely on MailChimp or any other platform for anything that needs time bound and reliable delivery. You might as well collect people's phone numbers and call them instead.

People have been foolishly saying for a long time that "email is dead" every time they see a new social network or a chat platform, but I'd say that "mass email is dead" for most people (personal emails, small businesses, organizations and small communities) without them even knowing what went wrong or what they could do to change things.