[sofixa]

Alternatively, communications fatigue. How many emails does the average employee get with nonsense that doesn't apply to them? Oh cool, we have a new VP. Oh cool, that department had a charity drive. Oh cool, system I've never heard of is getting replaced by a new one, favourite of this guy I've never heard of.

Add in the various spam (be it attacks or just random vendors trying to sell something).

At some point, people start to zone out and barely skim, if that, most of their work emails. Same with work chats, which are also more prone to people sharing random memes or photos from their picnic last week or their latest lego set.

[kmoser]

Everybody gets important emails, and it's literally part of their job to filter the wheat from the chaff. One of my benchmarks for someone's competency is their ability to manage information. With a combination of email filters and mental discipline, even the most busy inbox can be manageable. But this is an acquired skill, akin to not getting lost in social media, and some people are far better at it than others.

[BenjiWiebe]

If the same internal sender sends both irrelevant and important messages, it'll be pretty hard or impossible to filter.

My #1 method of keeping my inbox clean, is unsubscribing from newsletters.

[Marsymars]

Our HR lady took personal offence when I asked to be unsubscribed from the emails about “deals” that employees have access to from corporate partners. :(

[Vilian]

You can set custom rules in thunderbird to deal with specific mails, like tagging it as a "sale" or just deleting it based on regex

[Marsymars]

Yeah, I ended up doing that with Outlook.

I also set up a rule to auto-delete phishing test emails based on their headers, which annoyed the security team.

[kmoser]

Yes, the last filter is always the human being who has to deal with whatever the computer couldn't automate. But even then, you should be able to skim an email and quickly determine its relevancy, and decide whether you need to take action immediately, can leave it for the future, or can just delete it. Unless you're getting thousands of emails a day, this should be manageable.