In the question "Can I safely wait in the transit area of a destination airport for my visa to be approved?", OP explores the idea of traveling on an electronic visa which is not yet issued.
This rather risky venture got me curious. The unanimous consensus here seems to be that the airline will check OP's visa status and thus deny him boarding. I certainly do not mean to dispute this assertion, this is a question of legitimate curiosity.
How exactly do airlines do this? There are dozens of governments in the world that issue electronic visas. Do airlines have computer systems that interface with the internal databases of these governments, to check whether each traveler has a valid electronic visa at any given time?
Or do the airlines simply demand that the traveler show a print of the email they got when the electronic visa was approved, or something like that? Needless to say, such an email is rather easy to forge if no electronic check is made.
In "Do airlines verify the validity of visas electronically during check-in?", the answer seems to be "no", but that is for normal visas, that are printed on paper, with all the security features that would offer.
How do airlines check whether a traveler has an electronic visa?
I have tried searching the web in order to answer this myself, but the large number of irrelevant results has been too large for me to trawl my way to the answer.