We have established that emails are turning up but they are taking about 30 minutes from sending to arrival and similar when he sends them.
Yes you are of course right about the plus and minus signs but I still reckon his service provider has a problem with traffic today if it's taking that long. That is why I suggested seding himself an email to see what the timing was like and remove other SPs problems from the equation. I know the interweb isn't that simple but it usually helps me to identify who to shout at.