tmdry said:
while on the phone getting their info, I simply ask:...and your email is....
If this works ... great. BUT "reports from the field" tell us that more and more people are reluctant to give up their e-mail address with a "Valid Business Reason" (VBR) behind the request. (Heck, I don't normally give away my e-mail addy when booking a hotel room. I just say "No, why don't you just give me the confirmation number over the phone now?")
So now I recommend adding a VBR as an excuse for your request. The one that seems to work the best is AFTER getting all of their information is to use a "Colombo close" as in, "Oh, by the way Mrs. Jones, I almost forgot. I'd like to send you a checklist of how to get your home ready for your carpet cleaning. Do you have an e-mail address and I'll send the checklist off right now?"