We have now upgraded the SSL certificate with a new certificate from Letsencrypt. This certificate will auto-renew every three months. This is now automated and should not again expire like we have had today.
We have reverted to StartCom due to some issues with some clients complaining about the certificate, but we will test again soon. Just now we are back to StartCom for Ejabberd. On the website we still use Letsencrypt.
I have just added the latest CVS version of the Yahoo transport and it seems to be working from my initial tests. Please have a look at it and report findings. To make it work I removed all the old registrations on it, so you woul have to re-register the transport on your account.