[vel0city]

I've self-hosted email systems for businesses for nearly 20 years. I've actually had far easier times delivering to Gmail/Workspace clients than Outlook. Outlook constantly breaks strict DKIM with some of their protection scanning nonsense for emails that seem to get good deliverability almost everywhere else.

[BenjiWiebe]

Exactly. Outlook is the main source of deliverability headaches.

[expedition32]

Isn't that a good thing? I'm quite happy with Outlook filtering out trash.

[vel0city]

No. It will do things when shuffling the email through its various scanner platforms that will make their systems think the original sender is outlook's systems. So then when their later downstream service looks at the email it's like "cool an email from Outlook, let's see if Outlook is allowed to send for this domain...hmm...seems like outlook isn't allowed to send and I'm supposed to reject emails coming from unapproved senders so rejected!"

The way it sometimes bounces emails around in their own systems lead to them sometimes mixing up who actually originally sent the message. This causes all kinds of problems and seems entirely unique to their crappy setup.

[BenjiWiebe]

In our case, we're a small business, and we don't do email marketing. So I'd say that anything of ours that gets dropped by Outlook isn't trash. The only non-hand-typed email we send are transactional - actually transactional as in "here's your invoice" or "here's you're tracking number".

You know, you could achieve 100% spam filtering by just deleting every email. You wouldn't see any spam at all!