Despite what you seem to think, I am not stupid.
I admire your persistance in trying to get me to slip you into the country under my hat, (that phone call yesterday was brilliant!) but I simply cannot issue you a letter of invitation for your visa application... and I certainly cannot send it via an email attachment to your yahoo address.
I don't mean to be insulting, but I find it difficult to believe that your university in a third-world country could afford to send three of your students to a small-potatoes conference in southern Indiana (that has absolutely nothing to do with their reported field of study), especially given the fact that, as the "Dean" of your school, you can't even afford to get your own free, web-based email account, and are forced to share the same one with your "students".
However, I appreciate your efforts, and I want you to know that they have provided me with small moments of amusement in what might otherwise have been a rather boring week at work.
(Posted with permission from a locked entry by kendokamel.)