High Volume Bulk Email: Key Ingredients for Good Deliverability

January 15th, 2018

How do you ensure your messages make it into your recipients’ INBOXes?

Deliverability is key to anyone sending newsletters, announcements, notifications, or any other type of bulk email.  As a provider of premium and bulk email services, we constantly advise customers on how they can legitimately avoid having messages marked as spam and ensure that they are not black listed. In this article, we consolidate our advice for everyone’s benefit.  This includes: ensuring you have a good mailing list, maintaining your mailing list, email message content, and reputation management techniques like SPF, DKIM, and IP anonymization.

Step 1: A Good, Clean Mailing List is Essential

The number one mistake that we see is people wanting to use a poor quality mailing list.

LuxSci, like other legitimate bulk mail providers, requires that your mailing list contain only recipients who have explicitly opted to receive email from you and that you abide by the CAN-SPAM Act.  Doing anything else is likely to get you blacklisted and to have your account terminated for violations of your provider’s terms of service.

What does “explicitly opted to receive email from you” really mean?

  • The recipient actively and knowingly chose to become a member of your mailing list.

E.g. this could be by:

  1. Actively checking a check box in a form on your site (a subscription form or an option when they are placing an order). NOTE: these check boxes should not be pre-checked unless they person must also confirm the subscription in some other way.
  2. Becoming a customer or business associate of yours, where they have an expectation of getting mailings from you.  You should always provide them an opportunity to not receive your mailings.
  3. Signing up in any other way — like a physical sign up sheet or card at your physical office
  4. Sending you an email or text message requesting that they be added to your mailing list

In every case, you should keep a clear record of how the person’s address was opted into your list (in case they complain later).  If they complain and you have no idea how they were added … then how can you prove that it was an actual “opt-in”?

Poor mailing lists contain recipient email addresses that were:

  1. Taken from web site pages (manually or by automated “spider” processes)
  2. Purchased from a third party. Why? Even if the people on this list opted in to it — they certainly did not intend to opt in to mailings from whoever might buy it!  Purchased lists are a “big no no” in the industry.
  3. Copied from a membership directory where you are just another member.  E.g. it may be OK for a Chamber of Commerce to send a bulk mail to its members, but it is NOT OK for one member to send bulk email to the other members.
  4. Made by guessing addresses (e.g. sending to “joe@gmail.com” and “john@gmail.com” because they look like likely valid addresses)
  5. Found to be “Spam Trap” addresses — e.g. addresses that were created and added (as bait) to a web page or other location and never used for anything else.  Any messages actually sent to them must be non-opt in by definition and the address was added to the list  in a “poor” way.
  6. Contain many addresses that are invalid and which always bounce.

You should do everything you can to ensure that you mailing list is fully opt in and contains no addresses that are “poor”.  If you are unsure about a recipient’s address, do not use it. Furthermore, if you are violating CAN-SPAM, there are significant penalties:

Each separate email in violation of the CAN-SPAM Act is subject to penalties of up to $16,000!

The Canadian Anti-Spam laws are also very, very strict.

 Step 2: Mailing List Maintenance

Once you have a good opt-in mailing list and start using it, it is essential that you actively maintain this list and keep it updated.  In addition to adding new opt-in subscribers, you must:

  • Remove addresses that are invalid, no longer functional, or failing to deliver
  • Remove addresses of people who have requested to be opted out of your mailings
  • Remove addresses of people who have “marked your email as Spam”

Each of these tasks is very important; here is why:

Removing failing and invalid addresses.

Many email providers actively track the number of messages that you send to invalid recipient addresses on their servers.  If you send to “too many” of these (the threshold varies widely), these providers may temporarily or permanently block your messages.  Why?  Because sending to lots of invalid addresses is characteristic of mailings to purchased lists and to list of addresses that are “made up” or scanned from web sites.  Also, a sender with a good opt-in list would not be sending to invalid addresses

Many bulk email providers provide you with an easy way to get reports of what addresses are failing and why.  Use these reports to prune your lists.  (LuxSci offers this feature).

Honoring opt out requests.

When a recipient uses your opt out mechanism to remove him/herself from your list, you must ensure that that address never gets any more email from you and that that removal is effective very quickly.  This is required by the CAN SPAM act and by proper net behavior.  Additionally, if you continue to send to people who have requested opt outs, these people are likely to complain to their ISPs and to other organizations and you are likely to get black listed.

Remove addresses of people who have “marked your email as Spam.”

A large number of recipients will not use your “opt out” instructions to remove themselves from your list.  Why?  Because either (a) they are lazy, or (b) they assume that use of these instructions will confirm their email address and actually result in your sending them more “unwanted email”.  Instead, they use their email provider’s “mark as spam” feature to delete your message and hope that their spam filters block future messages from you.

If you can determine what recipients have done this and proactively remove their addresses from your mailing lists (as if they had oped out), your mailings will stop going to recipients who you know do not want them and will annoy fewer people — greatly lessening the chance of recipients complaining about the receipt of unwanted email and thus the chance of being blacklisted.

Note that recipients will mark messages as spam and complain about them if they do not want them … no matter if they are properly opted in or not.  That is the nature of the way people currently interact with email.  Your goal is to ensure that your messages make it to those who want them and also that they DO NOT get to those who do not want them.  Not only does this make your mailings faster and more efficient, it also helps eliminate complaints and improves your mailing reputation.

LuxSci has feedback agreements with many major ISPs.  We automatically collect all reports of messages recipients at these ISPs (e.g. AOL, Hotmail, MSN, Rackspace, Comcast, etc.) have marked as Spam and provide these reports to you so that you can proactively remove them from your lists. We also use this information to detect senders that generate excessive numbers of complaints….

Fixing old or poor mailing lists

Customers and prospects often tell us that they either have a “very old (years old) mailing list” or a one that is “opt out” instead of “opt in”, or some other mailing list with many “poor” addresses on it.  They usually are seeking advice on how to validate the list.  That is:

  • Find out what addresses are now invalid and remove them, and/or
  • Get permission from the recipients on the list for future mailings

The problem is that the current list is already poor and sending any kind of bulk mailing to it for any purpose … even to ask if the recipients would like more mailings from you in the future … is a violation of most company’s terms of service for bulk mailing.  It is, by definition,  sending bulk unsolicited email.  If you find yourself in possession of such a mailing list, the best thing to do is to either:

  • Discard it altogether, or
  • Validate which addresses are good through some means other than sending them an email.  E.g. by cross referencing with current customer lists or other means, if appropriate.

Message Content is King

So, now that you have a good mailing list and are ready to maintain it and begin sending bulk email messages, you must consider the content of the messages to be sent.  We very often find email messages that are blocked or denied due only to their content and not due to any kind of blacklisting.

Keep the following in mind:

  1. Keep the messages concise and use clean and simple HTML if you are using HTML markup
  2. Do not generate your email messages or email signatures in Microsoft Word
  3. Avoid poor spelling and poor grammar in your messages
  4. Clearly indicate why the recipient is getting the message and how s/he may opt out
  5. Clearly indicate your organization’s name, physical address, and other contact information
  6. Try to avoid using links to third party web site pages in your messages which may have a poor reputation.  Messages are often denied based on the web site address links.

Sending Reputation Management

Beyond your email message content and mailing list quality, there are several additional factors that play into the deliverability of your email.

Your email server’s IP address reputation.

If you are sending from an email server that is known to send lots of spam (e.g. maybe it is blacklisted already), then your recipients may block your messages through no fault of your own.  Poor sending reputations can occur:

  • If you are sending from an email server used by others and where those others are sending Spam or to poor quality mailing lists
  • If you are sending through your ISP’s mail server and your ISP is lax about sending spam.
  • You have been sending to a poor quality mailing list
  • You have been sending a lot of email with spam-like content

You can addresses IP address sending reputation by:

  • Using a mass mailing provider that is very strict about terms of service and about shutting down customers who are not abiding by proper bulk mailing practices.
  • If your IP at your ISP is on blacklists, then send through a bulk mailing provider that can hide this bad IP from your recipients (e.g. see LuxSci SMTP Anonymization)
  • Obtain a dedicated IP address for your sending (e.g. through a dedicated server).

Manage sending reputation with a dedicated IP

Note that getting “many different IP addresses to rotate through” is not a solution — that is merely a mechanism Spammers use to spread out their bad behavior across many IPs so that the effect of inevitable blacklisting is somewhat minimized.  In the past people had used this technique to try to improve deliverability.  Now-a-days, especially with the extreme shortage of IP (v4) addresses in the world, no legitimate mail provider will be able to provide blocks of IP v4 addresses to a single customer for the purpose of bulk mailing, under any conditions…. its just not permitted by ICANN.  The best you can do is to have one dedicated IP address per dedicated server that you utilize.

SPF. Adding “Sender Policy Framework” DNS records is useful as they allow recipients to verify that the messages you are sending are coming from a server approved to send email for your domain.  Hence, the messages you are sending are not fraudulent and perhaps are a little less likely to be Spam.

DKIM. DomainKeys Identified Mail, like SPF, helps differentiate legitimate email from fraudulent email and can also help with deliverability to certain providers who validate DKIM signatures. LuxSci’s High Volume  Outbound SMTP supports both DKIM and SPF.

Reverse DNS. The IP address the your mail server uses to send outbound email needs to have a “Reverse DNS”.  E.g. if you ask “what server belongs to this IP” … there must be an answer and that answer should match the domain name that that server uses to identify itself.  This is the responsibility of your bulk mailing provider (LuxSci takes care of this automatically) — but if it is setup incorrectly or missing, you will have significant deliverability issues.

Ramping up sending. If you want to send a LOT of email messages (hundreds of thousands or millions at once), it is best to start be sending smaller blasts to subsets of your recipients.  Gradually, over a few weeks, build up to your full mailing size.  Especially if you have a “new clean IP”, recipient mail servers may see a sudden large jump in mail from your IP or mail from your domain as a red flag indicating sudden spamming.  By actively ramping up, you effectively “warm” your IP address and get the recipient systems used to seeing email from your organization and for it not be not classified as spam by end users.  So, when you start sending to the complete list, the messages will be more readily accepted.

See also: Warming up your IP address automatically

Guaranteed Deliverability and White Listing Agreements

Many potential customers ask if we can “Guarantee” delivery of their messages to the INBOX of recipients at major ISPs like Gmail, Yahoo!, etc.   This obviously would be desirable.  Marketing language on some bulk mailing company’s web sites also seems to indicate that such agreements are possible and that only they can provide them.

In general, there is no way to guarantee delivery to anyone’s mailbox and in general the only “agreements” that major ISPs have is to allow senders to get feed back reports of messages marked as spam by their users.  These feed back agreements (which are sometimes even called “white list agreements”) typically contain explicit statements.  For example:

  • Gmail states: While Gmail works hard to deliver all legitimate mail to a user’s inbox, it’s possible that some legitimate messages may be marked as spam. Gmail does not accept ‘whitelisting’ requests from bulk senders, and we can’t guarantee that all of your messages will bypass our spam filters.
  • Verizon’sWhiteList Form” states that applicants “…agree to abide by Verizon Online’s policies and requirements regarding whitelist status and acknowledge that nothing herein guarantees delivery of mail originating from a whitelisted address or domain.”  I.e. it is really an application to a feedback loop and not an actual “white list”.


If you have read this entire article, you will see that there is no deliverability guarantee and that ISPs would never want to make such guarantees as that would open the door to having their users being forced to receive Spam and other unsolicited email (no ISP would want that). The best you can do to ensure good deliverability is to adhere to as many of the above guidelines as possible:

  1. Use of clean, well-maintained opt-in lists
  2. Sending clean, concise, well-formatted, and well-written email messages
  3. Using a reputable bulk mail provider that helps you determine failing recipient addresses and recipients who are marking messages as spam
  4. Using DKIM, SPF, and other techniques to bolster the reputation of your messages and to help recipients differentiate your legitimate mailings from forged ones.