I am having very similar issues and have been for at least a few months.

I'm sending single email to text SMS messages (not group messages).  When they are not received at #@vtext.com or #@vswpix.com  no error message is sent back to the sender.

I have access to a few email accounts from different domains so I ran an experiment.  I sent a very short text message and these are the current results:

From two different email accounts hosted at Dream Host:

No SMS text messages received at either #@vtext.com or #@vswpix.com

From an email account hosted at Tucows:

No SMS text messages received at either #@vtext.com or #@vswpix.com

From an email account hosted at 4securemail.com:

SMS text messages successfully received at both #@vtext.com and #@vswpix.com

From an email account hosted at MD OfficeMail:

SMS text messages successfully received at both #@vtext.com and #@vswpix.com

This is getting very tiresome and I see similar issues going on for 5 years on this forum...

Thanks for any and all help to resolve.