[kpcyrd]

Also a cool way for a spammer to verify if somebody is receiving those mails.

[ascagnel_]

True, but that's a low- to no-value lede; you're not very likely to sell to someone that's actively trying to avoid you.

[jonknee]

Who cares if they are receiving them and never seeing them because they are blocked?

[detaro]

Someone who easily can send other mails to the now verified address from somewhere else?