Email Just Barely Works
Est. reading time 1 minute
Email is not reliable. The circuitous path that email traverses would make Indiana Jones choose a new line of business. 
A "good chance" is what email has of arriving at its final destination — here's why.
Internet vs Email
Once an email has left your computer it takes on the Internet. This assumes that your ISP (Internet Service Provider like Shaw, Telus, etc.) accepts your email for processing after having passed a spam filter, volume throttle, and any other collection of tests they apply to try and squash non-legitimate email (as known as spam). Once the primary email server accepts your email, it quickly hands it off to the next email server. Your email will now pass through one or dozens more email servers — any one of them rejecting it for all kinds of reasons.
The reasons delivery could fail are more numerous than those that guarantee delivery. Fails by each email server or ISP range from reasonable to extraneous, making tracking down a fail difficult. Most of these 'fails' will send you back a notice that your message has been rejected, but it is not always true or clear as to why.
Recipient vs Email
Should your email pass these various tests and checks and traverse the Internet wilds, it may end up on the destination email server. Upon arrival it needs to pass a few more tests like spam filters and virus scans, and then on to the recipient's computer. The recipient's computer might also sort that email into a particular Inbox folder, which may cause the email to be lost.
So when you contact your email service provider and ask "where's my email?", well, honestly, it could have gotten stuck in a great number of places. Communicate directly with the sender or intended recipient to keep your business moving. If you are certain about a missing email, the most efficient use of your time is to share what details you can with your provider and allow them to investigate.
Thought you should know — happy emailing!