Opt-in
A list of email addresses whose owners have given permission to receive email
A list of email addresses, for example one used to send a newsletter, is described as
opt-in if the owner of every address has given permission for the address to be used for
the particular purpose.
Sending commercial and/or bulk email to addresses whose users have not opted in is
considered unethical and is illegal in many countries. Most countries require the lists to be
double opt-in or confirmed opt-in (COI): in this case the owner of the address
is sent a confirmation email that requires a response from the user before their address will be included
in the list.
Since it is easy to fill in someone else's email address in a web form, the use of COI
lists is generally considered best practice; commercial email sent to other lists is commonly believed to
be spam.
See also: opt-out.
