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Second part of our series on how ISP's (in this case Hotmail/Microsoft)decide what is and what isn't spam. An excellent inside view on how to increase email deliverability.

At the inagural AOTA Email Deliverability and Trust Academy conference in Seattle, Hotmail insider Krish Vitaldevara shared the top 5 reasons ISP's block email. His message boils down if you don't want to be treated like a spammer - don't act like a spammer. I'll cover today the number one reason they block email:



REASON # 1 Sending Infrastructure - the problem is in essence your email does not clearly identify who you are. Steps to remedy this:

• Authenticate/Publish your domain authentication or Sender ID. This allows the ISP to look to see if the domain your sending from is authorized to send mail.This process is called Sender ID.
  

• Separate traffic by brand or type of email. Each brand should have it's own IP address. Furthermore you need to separate the traffic. Transactional emails, i.e. order confirmations, shipping updates need to be separated from newsletter or marketing email.

• Send mail from the same IP's with consistent volumes and frequencies - ISP's don't like surprises - if they see a new IP or a not so new IP that has a jump in volume that's a warning sign for them to block or at a minimum severely throttle your traffic. This issue is especialy a problem for holiday mailers who should not introduce new IP's just before the season

• Ensure effective bounce management for both hard and soft bounces - bounces take up extra resources of ISP's. If you have a large number of bounces that can be an indicator that you have poor list management practices. ISP's then take the easy route and block your email. In general a hard bounce should be removed after no more than three delivery attempts. Soft bounces should be removed after no more than eight delivery attempts.
  

• Add "list unsubscribe" header offering subscribers a clean way to opt-out. This is the hardest thing for a marketer to do - to make it easy for a prospect or customer to leave. Unfortunately if you make it hard then they'll use the ISP email interface and click on the "THIS IS SPAM" button. If that happens repeatedly then you are more likely to be blocked.