One client wanted to take their site live on a weekday. I usually take sites live just before or after work hours on Friday in case there is a hiccup so business won't be interrupted.
This client also had chosen to host their email with Business Catalyst. BC actually employs a third party for email which partners cannot directly access.
Because we had never before taken a site live mid-week we were unaware that the email provider severely limits the number of outgoing emails for the first 24 hours to guard against spammers. Our client's email was pretty much shut down after a couple of hours because he had reached the limit. He was unable to conduct business.
I contacted support via online chat, described the problem and within an hour had the email provider increase the limit for the rest of the day. The client was able to continue his work and I looked like a hero. Yay!