push.boxcar.io broken again, still causing bounce messages

All mail addressed to @push.boxcar.io is, once again, bouncing. Unfortunately Boxcar’s SMTP servers are still misconfigured to return a “554 Transaction Failed. Too many connections” which causes bounce messages to be sent whenever a user using Boxcar’s services receives an email.

As a result, we have ceased delivery to this domain until such time as Boxcar gets their servers running again.

If anyone from boxcar reads this, please PLEASE fix your SMTP servers so that they return a proper SMTP code (might I suggest 421) to avoid the unneeded bounces.

Lastly, if anyone can recommend a useful alternative to Boxcar for sending notifications to iOS devices, please let me know and I’ll publish your recommendation.