Definitely a scam, I was working in Nigeria and had to fly to London to get my visa when I changed jobs as it could not be done in Nigeria.
For anybody else who is dealing with employment, NEVER EVER SEND MONEY, especially to Africa, no decent company will ask you to pay for your visa to go to work, as they have to sponsor you!!!
Furthermore, check the email address, @diplomats.com could be set up by anybody, official websites would usually be @____.gov
If in doubt, go to the country website and look at the other departments contact email address and compare.
Please don't get so desperate that you get stupid or careless!!!