Deliverability is the ability of an email to reach the recipient's inbox.
Sending a campaign does not guarantee that it will be visible to your recipients. Email providers such as Gmail, Outlook or Yahoo analyse each email in order to determine whether it deserves to be placed in the inbox, in the promotions tab or in the junk mail folder.
Several factors influence deliverability:
the quality of the contact database
the use of a sending domain
the subject line and content of your campaign
recipient engagement
the unsubscribe link
the size of your campaign
Good deliverability improves the visibility of your campaigns, increases open rates and maximises the results of your marketing activities. Conversely, if your emails are filtered or classified as spam, their impact becomes severely limited.
