Emails are not delivered to a mailbox in Plesk: DATA REPLY:452:4.2.2 Mailbox full

Symptoms

• Emails are not delivered to a mailbox.

• The following message is logged in
/var/log/maillog:

  DATA REPLY:452:4.2.2 Mailbox full

Cause

Mailbox size has reached the limit.

Resolution

1. Log in to Plesk.

2. Go to Domains > example.com > Email Addresses > john_doe@mail.com.

3. Change the value in Another size field.