Our POP3 mail servers on our shared hosting plans are configured to prevent too many logins per hour as a measure to smooth out demand on the server.
Presently, after 120 logins to your mail per hour, per user, you will be blocked access temporarily. This block lifts at the next hour boundary, so for example, if you were checking mail every 15 seconds, after 30 minutes you'd have logged in 120 times and be blocked for the next 30 minutes.
To avoid the block, configure your mail client to check mail no more than every 30 seconds or perhaps every five minutes. Do you really need to check mail so often?
You may also want to use IMAP instead of POP3 to check your mail. IMAP on our servers support the IDLE protocol so that mail is pushed to your mail client when it's available rather than your mail client having to check every n minutes. IMAP IDLE is very useful with mobile phones where it saves battery life if supported by your phone's email client software and allows you to share your mailboxes across multiple devices.
© 
