When your email open rates have been consistently low for a long time, Internet Service Providers (ISPs) like Gmail and Yahoo will consider your mail "unwanted" and begin to place your emails in the spam folder. This can hurt your deliverability and sender reputation.
In order to achieve good deliverability, you need to have consistent open rates above a certain threshold (anything over 15% is usually to be considered good). This shows that your email is wanted by subscribers and deserves to be sorted in the inbox.
To help improve your deliverability rates, we recommend using the Engagement Management tool to clean your list and remove unengaged contacts. Unengaged contacts are subscribers who have not open or clicked your email over a period of time you specify.
You can also track the engagement of your subscribers by implementing the Engagement Tagging automation recipes. These two automations work together to tag contacts as Engaged, Recent activity, Disengaged, and Inactive. This automation does not remove contacts from your lists or account.
For more information, read the “How to improve your open rate” help article.