Often the content or structure of an e-mail causes ISPs and spam filters to falsely identify a permission-based e-mail as spam. The definition of spam is actually also changing. A part of the public sees all unwanted e-mail as spam, even if they have opted-in to receiving them. If the senders IP address has a poor email reputation, the deliverability rate suffers and emails can also be classified as spam.
Definition of Deliverability
Deliverability refers to ensuring email messages are delivered to the inbox and aren’t blocked or rerouted by spam filters. It is an ongoing battle for email marketers to avoid being classed as spam. Successful deliverability depends on a combination of best practices, including authentication and email reputation.
A deliverability rate is a way to quantify the predicted percentage of e-mails delivered to the inbox. Not to be confused with delivery rate, which is the numbers of e-mails sent minus the number of emails returned, bounced or otherwise monitored not being delivered to the inbox.
Factors affecting Deliverability
Deliverability is affected by factors such as CAN-SPAM compliance, sender reputation, data Hygiene, whitelisting, blacklisting. But also the number of active subscribers and open and clickthrough rates can influence reputation with certain ISPs like hotmail or gmail. The rules of deliverability are constantly changing though.