It's likely an issue with your email spam server. If your IT security didn't white list all the IPs that Marketo requests, you may have to contact them about setting up some filters to allow key words in your From Name to come through. for example, we had our team set keywords for our company name versions so that we could use them in our test emails to ensure our html versions of tests made it through the system. Worth a try anyway.
I called support with the same issue. I'm supposed to launch a campaign this morning and was testing the email for a final check. I'm concerned about sending any emails out until it's resolved. Hopefully, it'll get resolved soon!
Ashley and Esther, I just tried to send an email about 15 minutes ago. The status is "pending" for all members of the campaign so I guess it spreads beyond just tests and alerts....hopefully it will be fixed soon!
Real-time update: I just received all of the test emails I tried to send earlier and the email has now been delivered to many members of the campaign....maybe it's fixed!