[Njtechdiv] Thunderbird return receipt

[Mario]

I'm trying to help someone out with solving a problem. she is using the 
latest version of Thunderbird, and when a return receipt is requested 
from her, she doesn't have enough time to click on the send button/link 
because the request goes away within a second. it's like the 
confirmation is automatic.

I've directed her to check the return receipt settings, but they haven't 
been changed since the installation of TB.

any ideas out there on how to solve this issue?

maybe there's another setting to take a look at?