Yes ("Disadvantage of this is that anyone who receives that mail will get registred without their consent if their mail client automatically shows images.").
If people do insist on using this method, they should at least add a prominent link to cancel the account in the e-mail.
But what if some random e-mail client prefetches the image and the e-mail end up never being read or whatever? This is not robust.
If people do insist on using this method, they should at least add a prominent link to cancel the account in the e-mail.
But what if some random e-mail client prefetches the image and the e-mail end up never being read or whatever? This is not robust.