How to send bulk email without spamming:

Solicited Bulk Email is an important mechanism for keeping consenting customers informed of products or service news. When Bulk Email is Solicited it is valuable to the recipient and therefore also to the sender. When it's Unsolicited it's purely Spam, an unwanted nuisance to the recipient, and, because it forces the recipient to assume the cost of receiving, storing and dealing with the unwanted advert it is also a theft of the unwilling recipient's time and resources.

The difference between senders of legitimate bulk email and spammers couldn't be clearer, the legitimate bulk email sender has verifiable permission from the recipients before sending, the spammer does not.

Spam
Opt-Out	All bulk email sent to recipients who have not expressly registered permission for their addresses to be placed on the mailing list, and which requires recipients to opt-out to stop further unsolicited bulk mailings, is by definition Unsolicited Bulk Email. The sending of Unsolicited Bulk Email is illegal in most of Europe and is against all ISP Terms of Service worldwide.
Unconfirmed Opt-In	The Recipient has, according to the Bulk Email Sender, unverifiably initiated a request for the address to be subscribed to the Bulk Email Sender's mailing list. The Bulk Email Sender has subscribed the address to the mailing list without verifying if the address owner has in fact granted permission or not. In most cases the Bulk Email Sender has simply purchased the address from another spammer. As there is no verification, all spammers claim to practice 'Opt-in' which is why the vast majority of spam claims you "opted-in". Unconfirmed Opt-in means that anyone can subscribe anyone, therefore if the address submitted by an unverified user was "President@Whitehouse.gov", the President has 'opted-in' and will receive bulk mailings whether he likes it or not until he opts-out.
	In case of dispute The Bulk Email Sender has no verifiable proof and is therefore liable for sending Spam, the sending of which is against all ISP contracts, against European laws, and against Spamhaus SBL policy.

Legitimate Bulk Email
Closed-Loop Opt-In	Also known as "Confirmed Opt-in" or "Verified Opt-in". The Recipient has verifiably confirmed permission for the address to be included on the specific mailing list, by confirming (responding to) the list subscription request verification. This is the standard practice for all Internet mailing lists, it ensures users are properly subscribed from a working address and with the address owner's consent.
	In case of dispute The Bulk Email Sender is fully and legally protected because the reply to the Subscription Confirmation Request received back from the recipient proves that the recipient did in fact opt-in and grant verifiable consent for the mailings.

Spammer-speak Tricks

Spammers and some Direct Marketing Associations fronting for Spammers try to further confuse the Bulk Email issue by using variations on the above terms, which have very different meanings from what consumers expect, these tricks include:

Spammer-speak:	Spammer's meaning
"Opt-In"	Wording used usually by spammers to mean the recipient "has not opted-out, therefore they are opt-in". Usually means any address the spammer can get hold of.
"Double-Opt-In"	Wording used usually by spammers to imply the recipient has "opted-in twice". The first time, says the spammer, was when the address was obtained and "opted-in" by the spammer without the recipient's consent, the second time was when the recipient failed to opt-out after receiving spam.
"Triple Opt-in"	Verbatim from Florida spam outfit Briceco Inc., who describe themselves as a "Leading provider of Marketing Solutions": "A triple opt-in email is a person who subscribes and fills out name, address, and interest." Presumably, a "quadruple-opt-in" is someone who fills out their age as well...