If you're a registered, opted-in user of Peachtree, and you unsubscribe from their emails, you could end up receiving this:
Our records indicate that [redacted] may have been inadvertantly [sic] opted out of e-mail communications.
If you did request to be removed, please click here to re-confirm your opt-out status.Uh, yeah, what? CAN-SPAM doesn't allow for any sort of "mail them again, make them opt-out again, and if they don't, that's affirmative consent" exemption.
Failure to respond is not the same thing as an opt-in.
When asking people, hey, do you really want to get our emails, it is 110% wrong to do so passively. By passively, I mean, when you tell people "take no action and we'll consider you opted-in." That's not best practice. That keeps your list full of spamtraps and people who don't want your mail. It builds no proof that people on your list actually want to be there. It logs nothing about proof of affirmative consent to address a blacklist or blocking issue.
But, you run into senders who complain about that. Oh noes, they say. My list will get smaller unless I assume everybody wants in, instead of requiring them to respond.
Yes, your list will be smaller, and it will be comprised only of people who actually want your email.
That's called respecting permission.