This can be due to any of the following reasons:

• Your account has reached the inactivity period. Free accounts are suspended after 7 months of inactivity and permanently deleted 5 months later (reference). Paid accounts are not deleted as long as payments are received. You can reactivate your account by upgrading to a paid plan.
• Your account has been compromised and has sent large volumes of spam emails, causing our anti-spam/anti-abuse system to block it.
• Your account was found by our anti-spam/anti-abuse system to be in violation of the Terms of Service.
• We have not received the outstanding subscription payment.
• There is a technical fault.

Whatever the case it might be, you can contact our support by email using the reset/notification email address (the one you used while registering your account at Mailfence) of the Mailfence account in question.

When you contact us, please don’t forget to mention your account username/email address and subscription package.

The procedure for unlocking Mailfence account may include additional user identity verification checks.