How to send an email from a DOS prompt using Telnet command line:
From your station or server do the following:
1- Open the DOS prompt
2- If you are in:
- Telnet to mx1-us1.ppe-hosted.com .Or. mx2-us1.ppe-hosted.com on port 25
- Telnet to mx1-eu1.ppe-hosted.com .Or. mx2-eu1.ppe-hosted.com on port 25
i.e.: telnet mx1-us1.ppe-hosted.com 25
3- wait till you get the banner "220 ........"
4- Type the following commands and wait to get a 250 or 354 after each command (screen shot below)
mail from: <email@example.com>
rcpt to: <destinationUser@domainDestination.com>
Subject: test mail flow
5- If the test message is received then the configuration is all set. ALL you have to do next is Switch your MX records to point to the proofpoint servers with respect to your location US/EU.