Use double opt-in lists: The difference between double and single opt-in is that with double opt-in (also called confirmed opt-in), people get a confirmation email after entering and submitting your form with their email address. They do not get subscribed until they click the confirmation link they receive on their email. Following are the advantages of using double-opt-in lists
- Deliverability rates for the lists that use double opt-in are significantly higher compared to single opt-in lists.
- Unsubscribe rates are lower than the open and click-through rates.
- Double opt-in lists reduce spam complaints.
Authenticate your emails with SPF, DKIM and DMARC: Email authentication protocols such as Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) help Internet Service Providers ensure that the email is from the company claiming to have sent it.
Authentication assists in addressing the problems of email spoofing and phishing and eventually leads to a reduction in the percentage of legitimate emails that are mistaken for spam.
Avoid using the same From and To address: Emails are marked as spam if both the sender’s and recipient’s email addresses are the same.
Don't hide the unsubscribe link: Include unsubscribing links in your emails to improve deliverability rates. If an unsubscribe link is unavailable or mislocated, there are chances that emails will be marked as spam.

To learn more about email deliverability, click here.