POP Access block due to mailbox full

POP Access block due to mailbox full

I am getting this error, can please rectify as want to use POP to download the mails and the remove from the account.

Task ' accounts@aag.my - Receiving' reported error (0x800CCC92) : 'Your e-mail server rejected your login. Verify your user name and password for this account in Account Settings. The server responded: -ERR Service Unavailable'