Undeliverable Email Addresse Primer

Thursday, February 18, 2016

Technology is ever evolving, and this is a good thing. Sometimes these evolutions cause hick-ups or a little more work than we desire, however in the long run it is more beneficial for us.

Recently we have discovered that there are several new anti-hacking and anti-spamming protocols/filters being put in place. Many of the top companies (i.e. Comcast, ATT, Verizon, etc.) have taken anti-spamming very serious and have enacted these new protocols.  This came about due to the recent increase of “Phishing” (http://en.wikipedia.org/wiki/Phishing) which simply put is hackers spam email inboxes with scams while posing as a real business by using their email domain (example: theboss@swissmango.com).

When an online newsletter is sent out to let's say 1000 recipients not everybody gets the newsletter due to a number reasons that are not related to the sending system. On the receiving side there are a number of blocks trying to stop any potential spam from getting thru to their mail server customers (among other things practices they use even before the mail reaches your mailbox. In many cases the sender is not notified of a bounce back or blacklisting of their email address or domain name, which makes them think that all emails reached their receiver list

We became aware of this situation at the start of the newer protocols, and began taking steps to remedy and continue to research the issue until we isolated it down to several steps we took immediate action on. Emails that end up in the “undeliverable” section of newsletter recipients should never just be revalidated without first knowing what caused them to end up there in the first place.  Below are several things we have found in our research.

  1. We use the services of a third party company that allows us to “whitelist” these emails for the newsletters. They have their automated procedures to ensure the best possible delivery of these newsletters. The newsletters are automatically divided into smaller batches so that these services don’t see 1,000’s of newsletters coming at one time.
  2. Sender Policy Framework (SPF) is an email validation system designed to prevent email spamming. We have enabled these SPF records for all our clients to help in this process of whitelisting.
  3. We have found also that several clients have quite several bad email addresses within their lists, and this helps to contribute to poor ratings & reputation (blacklisting).  Adding to our service is http://verify-email.org, an email address verifying system. We are working through our clients lists to help in this process. We also recommend that you help to do this on your own as well.
  4. Recently we made adjustments to our newsletter system to allow the export of all undeliverable email addresses. Then after these are verified as valid and removing the bad addresses we’re able to then import and revalidate them in one step. This will result in only the email addresses either not valid are only shown.
  5. If the email newsletters are rejected on the recipient side sometimes the organization that use enterprise solutions for their email system (example: school boards) will only allow emails to go through if they are allowed from their side. This is also related to the new SPF protocols. If this is the case you would want to contact this entity to have your email domain added the safe list.
  6. Recently we also added a new service for clients who have large contact lists to help ensure they stay whitelisted. Our third party service we use to whitelist also provides a dedicated IP address which would only be applied to a single client. By opting into this add-on you will no longer be on the shared IP address which has its own whitelisting procedure. As long as you follow best practices, this will result in you staying whitelisted for the foreseeable future.  This also helps us identify when extra help may needed for our clients.
  7. Once a week we run all IP addresses through filter checks to help ensure that our shared and dedicated IP addresses are not being blacklisted. If we find that they are being blacklisted we’ll take the proper steps to rectify this situation.


We are sorry for the inconvenience this might have caused our clients. We hope that this explanation might help you better understand what causes newsletters not reaching their intended. We strive to continue to provide the best possible service we can, and continue to research new protocol and filters to help alleviate any issues for our clients.

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