When I try to send a text email to someone, my text email option checkbox does not appear in the sample email window anymore. I did not change anything account-wise either.
When you're editing the email, try choosing the "Edit Settings" button at the top and checking off the Text-Only box. Now, when you send a sample, it should be text only.
I just poked around in Marketo - try previewing the email and selecting "Send Sample" there. There is a checkbox to also send a text-only version. If you choose to send a sample from anywhere else, that option is not there. No idea why - seems a bit silly!
Hi David -- Not sure if you've found a solution for this yet, but I experienced the same thing last week. The send sample email pop-up window can be expanded for height by dragging the edges of the box. Drag the bottom of the box to expand the height and the checkbox for the text version will be revealed.
@David - Don't feel silly... it's a bug, and the only reason I know that you can expand the window is because I contacted Marketo support about the same thing last week. 🙂