I'm a long time advocate of using expendable email addresses any time you have to give someone an email address (and then making sure you can turn them off or more broadly apply filters to them). However, some of the time I've trusted the people who were asking for an email address, didn't have an expendable address already prepared for them, and gave them my regular email address. Today I discovered (or realized) another reason to not do this and to use expendable addresses for absolutely everything, and it's not the usual reason of "the people you gave your email address to might get compromised and have their address collection extracted and sold to spammers". The new problem is mailing service providers, such as Mailchimp .

It's guaranteed that some amount of spammers make use of big mailing service providers, so you will periodically get spam email to any exposed email address, most likely including your real, primary one from such MSPs. At the same time, these days it's quite likely that anyone you give your email address to will at some point wind up using an MSP, if only to send out a cheerful notification of, say, "we moved from street address A to street address B, please remember for planning your next appointment" (because if you want to send out such a mass mailing, you basically have to outsource it to an MSP to get it done, even if you normally use, eg, GMail for your regular organizational activities).

If you've given innocent trustworthy organizations your main email address, it's potentially dangerous or impossible to block a particular MSP from sending email to it. In searching your email archive, you may find that such an organization is already using the MSP to send you stuff that you want, or for big MSPs you might decide that the odds are too bad. But if you've given separate expendable email addresses to all such organizations, you know that they're not going to be sending anything to your main email address, including through some MSP that you've just got spam from, and it's much safer to block that MSP's access to your main email address.

This issue hadn't occurred to me back when I apparently gave one organization my main email address, but it became relevant recently. So now I'm writing it down, if only for my future self as a reminder of why I don't want to do that.