Email messages are rarely lost in transit. Check again to see if the recipient has received your message; it is possible that the recipient has simply not responded to you yet.
If the message has definitely not been received, check the following scenarios:
Your message was not actually sent.
The only way to actually send a message is to click the Send button.
Sometimes you might finish composing a message and then surf to another
location before you click the Send button. Also, after you click the Send
button, watch for the "Mail Sent" confirmation message that
ensures that your email message was sent successfully.
Your message was not correctly addressed.
You might have typed a different email address than the one you intended.
For example, you might have entered a typo in the email address that changes
it into the valid email address of another user. In this situation, your
message would be delivered to the address you incorrectly typed and you
would not receive an error message.
The message was delayed.
While messages normally are delivered within a short time, they can
be delayed if they encounter heavy Internet traffic or routing problems.
(Sometimes, delays can last for several hours.)
Some other possibilities:
Interruptions or disruptions in email transmissions over the Internet
can occasionally make your email message undeliverable. The best solution
is to re-send your message.