If an email service provider is having a problem with some of their mail servers deferring connections with a 4.2.2 error code for an extended period of time try smtp routing email for their domain to their good servers. This should fix any problems with email delivery delays that the senders and recipients may be complaining about. I'd also recommend contacting the destination mail service problem in case they are not yet aware of the issue. Gathering information for the trouble report would be helpful for them, including some initial troubleshooting including showing if routing is OK and if you can get to port 25 and is closes or if you are not able to reach their port 25.
