This is very true today and I thank you for posting this. I can say that we are not lying when we say we didn't get your email, and this article helps us all understand why. 
Our web site currently receives an email sent to [anything]@mtu.com on the average every 3-5 seconds. It has been observed one a second at times.
Ladies and Gentlemen, that's up to 80,000 emails A DAY!!! Is there any wonder why our web site is sometimes slow? Do you understand why we don't always get your email? Our spam arrestor programs at our web site mail server and our local computers make heuristic decisions as to what is spam, virus, or good email.
However, depending on the words and subject you use, they may rate your email as spam or even a virus and we never even see it. 
We will soon move our mtu.com mail server from our web site to a spam filtering site to remove this MASSIVE spam email load from our mtu.com site to speed it up.
Example #1: We had a situation last week where a VERY KNOWLEDGEABLE fellow with his own web site was sending emails to us from his web site email address, and from another email address. We got the ones from the "other" address, but not from his web site address. MTUSUPPORT and he both scratched their heads for a while. He ended up realizing that something his web/server master is doing is blocking his emails going out... OR... being received when we responded to them.
Example #2: We had a situation with a customer in Mexico some months back. He emailed us 3 times, but we never got them. When he posted in the Forums, we saw his post and answered him, also informing him we never received his emails.
Example #3: As President of MTU, I sent an email to two of our MTU Staff members. Neither had received it 12 hours later. However, it did finally come in.
Example #4: We have received emails from the UK as long as 48 hours later than they were sent.
Any heavy used or free email service (
hotmail, msn, yahoo, juno, aol, freeserve, etc.) do very heavy filtering on all incoming emails to you. We often have proof we sent emails to users at one of these services, and it was never received. The "Download Instructions" email that our store sends when you order a software product is often rated as spam by AOL. We even removed the MTU.com from the subject because THEY TREAT ANY EMAIL AS SPAM FROM A .COM source!!!!!!!
If you use AOL... PLEASE... find another email provider!!!!!
When I do a Trace-route to our server, it shows about 20 computers that my email goes through to get to our server, and then the same number to return back to any of our Staff at MTU. If any one of these computers is slow or down, my email may take an alternate route through more computers. It takes time to get an email through all these computers!
