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Challenge Messages Are Blocked by ISP  -  KB Article #1317

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Some ISPs prevent your computer from sending any data on port 25 (the SMTP or outgoing mail port) to servers other than their SMTP servers. They do this to prevent the spread of worms or email viruses. They also do this to prevent you from running your own SMTP server. Zaep can get around this limitation, by relaying challenge messages to your ISP's SMTP server. To enable this feature follow these instructions:

  • Double click on the Zaep icon in your system tray next to your clock.
  • Select "SMTP" under servers.
  • Enter your ISP's SMTP server name into "SMTP Server Name/IP". This is normally of the form or
  • Enter the port number your ISP has instructed you to use under "SMTP Server Port". Port 25 is the default SMTP Port.
  • Select the "Preferences" option.
  • Enable "Relay challenges to SMTP server defined under SMTP Server".
NOTE: Enabling this option has a couple side effects. First Zaep will be unable to determine which challenges have invalid email addresses. Second you may receive messages from your server telling you the challenge was undeliverable. If this is the case you can either black list your ISP's email server or simply setup message rules in your email client to delete these messages. You may also be able to simply request that your ISP open port 25