Opt in Email

Opt in e-mail is a term that refers to promotional e-mails that have been requested by the individual receiving them. Unlike spam promotional e-mails that get sent out to large lists of recipients without regard to whether or not they want the information, opt-in e-mails are only sent to people who specifically request them.
Opt-in e-mails are targeted and often personalized and carry information about specific topics or promotions that users are interested in learning about. Typical opt-in e-mails contain newsletters, product information or special promotional offers. For example, if a user frequented a Web site that sold books and music online, that user could “opt in” to receive announcements when his favorite author or musician released new material. The promotional e-mail may even present the recipient with a special promotional offer to purchase the product at a discount available only to those on the opt-in list.

There are several common forms of opt-in e-mail:
Confirmed opt-in
A new subscriber asks to be subscribed to the mailing list, but unlike unconfirmed opt-in, a confirmation e-mail is sent to verify it was really them. The person must not be added to the mailing list unless an explicit step is taken, such as clicking a special web link or sending back a reply e-mail. The web link or reply e-mail must contains some sort of secret word or token that can not be guessed by a malicious person. This ensures that no person can subscribe someone else out of malice or error. Mail system administrators and non-spam mailing list operators refer to confirmed subscription or closed-loop opt-in.

Unconfirmed opt-in
A new subscriber first gives his address to the list software but not all the steps are taken to make sure that this address actually belongs to the person. This can cause e-mail from the mailing list to be considered spam because simple typos of the email address can cause the email to be sent to someone else. Malicious subscriptions are also possible, as are subscriptions that are due to spammers forging email addresses that are sent to the e-mail addressed used to subscribe to the mailing list.
Double opt-in
With double opt-in, the submitted name is not immediately added to a mailing list. Instead, an email is sent to the address, asking to confirm that email address should indeed be added. If the recipient of the confirmation email does nothing, the submitted address is taken off of any mailings. The name is only added to a distribution list if the recipient responds to the confirmation email.
Instead of giving people the option to be put in the list, they are automatically put in and have the option to be taken out.

Email marketing without permission represent a great risks. Anti-spam campaigns by most of the major Internet service providers (ISPs) such as  Yahoo!, MSN Hotmail and others have lead to an aggressive hunt for not only those responsible for spamming, but to penalize companies whose products are being advertised as well.

Most of the larger ISPs have written their own ?white list? of standards for permission e-mail marketers who are not spammers and wish to follow set anti-spam principles. Some popular ISPs have their white list guidelines posted on their customer service portions of their web sites, but those who do not will issue these guidelines upon request. This greatly reduces the risk for permission email marketers using opt-in email not to be blacklisted by their ISPs, while at the same time is catching spammers at the source and preventing them from using the ISP option for their outbound unsolicited email.