I was recently asked: "if you could give us a bit more information on the email attrition rates, also the common reasons as to why emails are often junked". 

Email attrition is where a proportion of a list is no longer usable due to the subscriber addresses being invalid. Addresses can become invalid for a number of reasons such as the subscriber changes jobs, or when a webmail address has been inactive for a long time. The attrition rates we see varies from list to list. We would expect the attrition on average to be about 15% per annum, but it can be higher. For example we'd expect to see a higher bounce rate for first time deployment to a list that had no confirm or double opt in email.

Reasons emails are junked really is a huge subject and is always changing. There are three main categories in understanding deliverability follow with some key points for each:

• Infrastructure
  • The set up of your sender domain and IP address has an impact on delivery. Any issues are usually easily resolved and is part of our normal service
  • Infrastructure includes (but not limited to) SPF records and domain keys, IP isolation and whitelisting
• Content
• • Content may be filtered at several points along the path of an email - by a firewall or spam appliance, by the mail server or at the local inbox
  • Content filtering varies between ISP's, corporate mail servers and even individuals
  • Testing eliminates most content filtering issues and should never be overlooked
• Reputation
• • Includes block lists which you can find yourself on if your list contains spam traps or if you exceed a threshold of complaints
  • ISP's evaluate subscribers behaviour towards a sender including the ratio of emails that are marked as spam, deleted without being read and whether recipients are even opening your email