SpamHaus.Org: Right way to send bulk email
- This is intended only as a basic outline of what it takes to manage a legitimate bulk e-mail list. Seek expert advice from appropriate companies and consultants for a more complete understanding of the complicated issues of legitimate bulk e-mail. Remember, all bulk e-mail must be opt in, otherwise it is unsolicited. And Unsolicited Bulk E-mail (UBE) is spam!
Address acquisition - Make sure it's Opt In. If the recipient didn't ask for it in the first place, the rest of the list management processes are irrelevant. While various transactions and business relationships can infer permission, if there's any doubt, or for any on-going bulk e-mail relationship, closed-loop Confirmed Opt In (COI) is the gold standard for verifying permission, in use since about 1997. Some examples of software which use COI include Majordomo-2, EZMLM, Mailman, and Lyris.
- Truth in advertising - State your policies and the nature of the bulk e-mail at the point of subscription. Tell the subscriber what to expect: how often, how big, what kind, what topics and content, etc. Don't hide information about the subscription on remote pages, behind hyperlinks, or buried in jargon, legalese, and obfuscation.
- Identify yourself, or at least your company or organization. Use properly registered domains with working mail and web addresses. Have a website at those domains which properly identifies your company. Don't hide behind ever-changing mazes of domains. Anonymized "whois" records just shout "hey, I'm trying to hide something!" Other technical means to identify your mail includes SPF and DKIM records in DNS and various sender reputation services. Make your online identity as solid as a brick-and-mortar business.
- Maintenance - Keep your list current! Remove unsubscription requests and bounces promptly, as close to real-time as possible, on the same day at least. Mail the list at regular intervals. Unmailed lists provoke high complaint rates when they reactivate, even from truly opt-in addresses. Addresses "churn" over time, that is, they are abandoned or re-used. For most commercial lists, mail at least once per week and remove any address with three sequential bounces, or with sequential bounces for more than two weeks.
- Bounce processing - Respect what the recipient's server tells you. SMTP "5xy" codes mean "No!" Bouncing your mail off the filters but showing up in the logs, or resuming spamming after filter rules come down, is a sure-fire way to really annoy server operators and mailbox owners alike. Addresses being converted to spamtraps will typically reject (5xy) all deliveries for about six months...you certainly don't want those on your list so make sure they bounce off!
Similarly, a receiver's TEMP FAIL response (4xy) should be respected by your server. All standards-compliant servers will automatically retry such deferred deliveries at increasing time intervals. Generally retries cease and the message is considered undeliverable after 5 days. The interval before pruning a deferred address from your list is usually longer and takes more bounces than a hard "5xy" rejection, but eventually such addresses should also be retired from your list.
- Unsubscription must work! Promptly. And for all the bulk mail you're sending to that address. It must work via e-mail (include correct info in headers) and many subscribers also appreciate a web link included in message body. Sign up for feedback loops, and consider that abuse reports may indicate more serious problems than can be fixed by simply unsubscribing the reporting address. Some jurisdictions also require unsubscription via snail-mail. Basically, if someone wants off your list, help them with their request no matter how they ask.
- Concurrency - Respect the receiving server's SMTP dialogue. If it says pipelining allowed, give it what it wants. If it says "try again later" (4xy), don't despair, let your server queue the message and do what good servers are supposed to do. If it accepts a bit slowly, throttle back your server so as not to flood smaller sites. Opening up lots of threads to a slow server is an excellent way to get tarpitted and blocked. (Good servers do all that stuff by default.)
- Seek expert advice! There are highly qualified delivery consultants, and some who aren't so qualified...buyer beware. Ask your ISP for advice. Consider a reputable E-mail Service Provider (ESP). If any delivery consultant is not aware of the terms and problems in this very brief outline, or if they make promises that they can get you "whitelisted" at ISPs, well, do you want to buy a bridge?