> How many emails just ended up going to a limited distribution list? Worse, many email systems have a retention period. (This is also a problem with Slack, mind you.)

I'm not saying that email is perfect and doesn't have its issues, I'm just saying Slack is worse.

The kind of use case I was thinking of is myself and others searching through our own personal archives for stuff (which people at my company use to get around server retention policies). That works with email but not with Slack.