Our customer emails was broken in a number of email clients and management kept asking me 'how, why & what'.
I explained that we had no software to test the code & how the emails would appear. I explained we could try and do it manually, which would take hours of my time, hire another developer to redo or, throw a little budget at the problem and get a Litmus account.
I showed management the angry customer complaints & broken emails, vs emails that displayed correctly (after some minor tweaks) in all clients almost instantly with Litmus! Simply amazing!