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What factors effect your email delivery?

Posted by Dave Zulu, Last modified by Peter Zulu on 25 August 2016 09:49 AM

The variables for ESP delivery are vast with no ‘one size fits all’ approach available. Each mail provider has their own view on what constitutes SPAM and set their environments up accordingly. This can be as individual as the view held from one employee to the next.

Weak SPAM laws in the US and other countries have meant email providers (hosts) and the ESP community have had to take matters into their own hands and created new technical hurdles for email configuration rather than tougher laws and education. These additional technical items provide security that the email is not unsolicited or of a criminal nature.

In short the following is required for bulk email to be delivered :

  •          Known IP Range with PTR and reverse DNS
  •          A MTA that ‘handshakes’ mail with  each host
  •          Email headers configured to hold key information such as:

o   Mail origin

o   Purpose

o   SPF record

o   DKIM record

o   Abuse policy

o   Plus several other key item

A new security record was added in 2014 called DMARC. Some mail hosts rely on this and others do not.

Once the technology is configured the next determinant is not so scientific. IP reputation and Sender Score determines how much mail gets through and at what rate. The following is the order in which the email community views typs of email (best to worst):

  1.        Day to day email
  2.        Notifications
  3.        Transactional email
  4.        Marketing (newsletters, product updates)
  5.        Affiliate / co-registration
  6.        Unsolicited
  7.        Spoof / Illegal / Phishing

If the technical items pass then the the way in which these emails are analyzed are as following:

  •          Sender Score – is the sender reputable (not the ESP)
  •          Volume of email being sent
  •          Reputation of IP addresses
  •          Content
  •          Complaint rate (must be <0.1% for every campaign sent) is compiled by recipients flagging an email as SPAM)


ESP’s like Zulu eDM invest heavily into IP reputation for our shared infrastructure. When a large volume senders comes on board with perceived poor content and a poor sender reputation the ESP runs the risk of losing their IP Address Reputation and Sender Reputation.

Zulu has been ahead of the game for years, advising our clients to target more and use the tools we have built to engage with recipients. Not only will your organization benefit, your emails wiil get a higher priority.


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