Often content or structure of an email causes Mailbox providers like for instance Gmail or Outlook.com and other spam filters to identify a permission-based email as spam. (The definition of spam is also changing.) Some email recipients consider all unwanted email as spam, even if they have opted in to receiving emails from those organizations. If the sender’s IP address has a poor email reputation, the deliverability rate suffers, and emails can also be classified as spam.
Deliverability refers to ensuring email messages are delivered to the inbox and aren’t blocked or rerouted by spam filters. This is an ongoing battle for email marketers. Successful deliverability depends on a combination of best practices, including authentication and email reputation.
A deliverability rate quantifies the predicted percentage of emails delivered to the inbox. This is not to be confused with delivery rate, which is the number of emails sent minus the number of emails returned, bounced or otherwise not being delivered to the inbox.
Factors affecting deliverability
Deliverability is affected by factors such as CAN-SPAM compliance, sender reputation, list hygiene, whitelisting and blacklisting. The number of active subscribers, open and click-through rates also can influence reputation with certain ISPs such as Hotmail or Gmail. Keep in mind that, like the definition of spam, the rules of deliverability are constantly changing.
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