Mail forward to MMS gateway not getting through

Mail forward to MMS gateway not getting through

I'm trying to forward email through an email-to-MMS gateway and the verification message isn't getting through.  What's happening is that a mosaic pattern graphic is getting through while the email text is stripped out.  Can the verification code messages be sent as just plain text instead of HTML-formatted messages?  When the email address is finally added, the confirmation notification message is sent as plain text.  Why not the verification message also?