After configuring emailgtw probe to send emails to one or more recipients, it is discovered that at least some of those emails don't arrive.
What can cause emailgtw probe emails to not arrive? Looking in the logs reveals the following type of statements:
May 30 12:00:00:354 emailgtw: RCPT TO:<email@example.com>
May 30 12:00:00:361 emailgtw: 550 5.7.1 Unable to relay
May 30 12:00:00:361 emailgtw: RCPT TO:<firstname.lastname@example.org>
May 30 12:00:00:362 emailgtw: 250 2.1.5 Recipient OK
The log tells the story here. The email server sends a response for both addresses. The address that does receive the email has an 'OK' message. The address that doesn't receive the email has a 'Unable to relay' response from the email server.
This tells us that the email server is unable to send on the email to the desired address. A change needs to be made on the email server to allow email to be send to this address. Provide this error message to your email admin and he can resolve the issue.