Using Greylisting to block spam and virus e-mails.
You came here probably after seeing a mail of yours being rejected with a message like this:
Greylisted for 300 seconds (see http://34.89.133.246/greylisted)
The mail server generating this error message is using a system called Greylisting to filter spam and viruses. It relies on Mail Servers behaving according to the standards and usually doesn’t require any action by the user. Your mails should only possibly be delayed.
See this page for a description of how Greylisting works.
The right contact address for problems with the sipwise.com domain is postmaster@sipwise.com.