Before I switched to fastmail, gmail would not believe me when I marked an email as not-spam. They would still get flagged. All I wanted was updates from one band.
That didn’t stop me from repeatedly getting junk from every other record label my email was sold to. It was an endless procession of shit I never subscribed to.
"Inboxing" with Gmail & Outlook is a baroque, hellish process for mailservers.
When either provider decides your small email server is sending spam (eg: sending an email with an attachment, or any kind of form email like a daily report) you won't get through to user inboxes, and instead you'll be routed to spam, or for Outlook.com hosted addresses they will accept mail from your server and send it to /dev/null. Gmail's process is bad, but Microsoft has decided to accept emails and throw them away (which is ridiculous).
At my workplace we have two email addresses, one from google mail (gmail for business) and one from MS Exchange.
I never had a problem with gmail for business regarding spam. I regularly receive mails from smaller businesses (some of them hosting their own mail server) and never had a complaint from anyone yet. Since i can also be contacted via phone i'd know.
On the other hand, MS Exchange constantly delivers obvious spam mails and (quite seldomly, but still) swallows legitimate mail.
Anectodal, i know. And disclaimer: the behavior depicted in the article is as bad as it gets, if everything is as described.
That didn’t stop me from repeatedly getting junk from every other record label my email was sold to. It was an endless procession of shit I never subscribed to.