If you get an error message in your email client software saying Your connection has been blocked temporarily - Try again later, this means the SMTP Intrusion Prevention System (IPS) in VPOP3 has detected abnormal behaviour from your IP address, and it has applied a temporary block to prevent abusive behaviour.

You can set how the IPS works by going to Services → SMTP → IDS/IPS in the VPOP3 settings.

Every time one of the monitored events happens (eg a failed login, or a message containing a blocked attachment name) the relevant 'multiplier' is added to a score for that IP address. If that score reaches the Client Error Block Threshold value within the specified Client Error Monitor Period, then the IP address is blocked for the Client Error Block Time time.

For instance, with the default settings of:

• Bad Authentication Multiplier = 50
• Bad Local Rcpt Multiplier = 50
• Relay Denied Multiplier = 100
• Client Error Monitor Period = 60 minutes
• Client Error Block Threshold = 1000
• Client Error Block Time = 30 minutes

If an IP address tries to relay through VPOP3 twice (2 x 100), tries to log on 5 times with an invalid password (5 x 50), tries to send to 12 local addresses which don't exist (12 x 50) within an hour, then the total score will be 200 + 250 + 600 = 1050, so that IP address will be blocked for 30 minutes.

You can see which events have happened by clicking on the View Event Log button

You can see which IP addresses have been blocked (and remove the blocks, or manually add blocks) by clicking on the Manage Block List button

You can add/remove addresses from a 'never block list' by clicking on the Manage Never Block List button.

Common causes of legitimate IP addresses being blocked are:

1. sending messages to invalid local recipients (eg if the email address is misspelled)
2. sending messages containing prohibited attachment filenames, eg attachments with 'dual filename extensions', such as 'document.xls.pdf'

NB - As of version 5.0d there is a known issue with the Manage Block List and Manage Never Block List buttons in Internet Explorer. Other web browsers, such as Mozilla Firefox and Google Chrome work correctly. This problem should be fixed in version 5.0e