Permission is express, verifiable consent to receive marketing communication.
Express means that when you asked for permission, your question wasn't tied in with another agreement. For example, a separate checkbox for "I would like to receive marketing email from XYZ company" is express and clear.
If enough people mark your campaigns as spam, the ISP can blacklist you. When that happens, any message you send to anyone on their network will be blocked.
Spam filters use a lot of different criteria to judge incoming email. Each factor is weighed and added up to assign a spam score, which determines if a campaign will pass through the filter. Passing scores vary depending on the server, so a campaign might pass through some filters but not others.
There are many steps you can take to avoid spam filters.
Definition - What does List Hygiene mean?
List hygiene is the process of creating, editing and maintaining a mailing list's email addresses, subscriptions and opt-ins. It ensures the clean dissemination of an organization's broadcasted email message to its related and operational email addresses/subscribers.
List hygiene is used in email marketing campaigns to create and manage email subscriber lists. The primary objective of list hygiene is ensuring that a broadcasted email message receives optimal engagement and conversion rates.
Rookie Email mistakes
Strategic planning
Definition of List
Creative execution
Integration of campaign with other channels
Personalization of the message
Deployment
Interaction handling
Generation of reports
Analysis of results