Way back when, I wondered aloud if 2015 or 2016 would be considered the year of DMARC. Maybe it's more accurate to say that 2020 was the year of DMARC as it seems to finally getting to that point where people assume that email providers support DMARC and that people are starting to understand that DMARC is something you ought to implement when configuring email sending from a given domain name.
Where does that leave us in 2021? There are still a lot of people who have yet to implement DMARC but I think that they're going to come around; as I note above it's getting to the point where DMARC is basically expected, so I think those that aren't yet hip to the ways of DMARC shall become hip soon enough. It feels like we've hit that tipping point.
At this point, I'm done listening to people complain about DMARC and mailing lists (discussion lists). DMARC is here, it caught on, deal with it. It is not hard to deal with in the mailing list context unless one chooses to be obstinate. I'm done arguing about it with people who want to do funny stuff like purposely rewriting headers to ".tld.invalid" instead of simply signing mail as the list owner and taking proper responsibility for the messages you relay and authenticating them properly. Technology evolves, and if you choose not to evolve with it, that's on you, not the world. (And the Authenticated Received Chain (ARC) mechanism for DMARC is so edge case that I'm not really sure you need to consider it any time soon.)
BIMI might be considered the next big thing. What BIMI essentially does is help drive DMARC adoption by allowing senders to display a company or brand logo associated with email messages in an email client, and it's currently active in beta on both Gmail and Yahoo Mail. I can tell from the number of questions that I get that lots of people are interested in BIMI. However, I worry that unless you're a big company with a well-known brand, you might end up locked out of BIMI. Gmail's closed beta requires a "verified mark certificate" with its own review process, cost and requirements, and it's an open question as to whether or not this will be required by Gmail in the long term, or required by other providers. Depending on how this pans out, it could end up being a barrier to entry for a lot of smaller senders.
Email mailbox provider consolidation isn't likely to be a thing this year, at least not in the US and not at the larger end. You've basically got a top four of Gmail, Verizon (Yahoo), Microsoft (Outlook/Hotmail) and Apple's iCloud mail. That's maybe 95% of B2C subscriber mailboxes right there -- go deeper than that and everybody else is too small to measure.
In the B2B realm, Proofpoint acquired Cloudmark (back in 2017), but seems to continue to run both brands as visibly separate entities. There's been other provider acquisitions (including Proofpoint's acquisition of Wombat) but once you look beyond Proofpoint, it feels like nobody has any significant market reach. Meaning that B2B deliverability remains an opportunity to get nibbled to death by ducks -- no easy way to wipe the slate clean; best to focus on prevention instead of remediation.
Mobile email is big and only getting bigger. Perhaps not strictly deliverability-related -- the email gateways and inbox placement metrics are the same ones we already know -- but it does speak to how content and rendering optimization is very important to email marketing success. If your email renders poorly on iPhone and Android, you're going to suffer. (I see the irony in this comment given that I don't yet use a responsive email template for Spam Resource.)
There you have it, my quick, off-the-cuff thoughts on what 2021 holds for us in email deliverability land. What have I missed? What would you strike off my list? What would you add to it? I welcome your thoughts and feedback.