Verified answer

First, check with the sender to make sure that they actually sent the message and aren't having problems with their mail server. If that's not the problem, it's possible one of the following occurred:

The message was not addressed properly.

The sender might not have your correct email address. Or, sometimes people make typos in email addresses, but the "incorrect" address just turns out to be someone else's correct email address. If this happened, the message intended for you could have been received by someone else.

If you're an international Yahoo! Mail user, the sender might have used the standard yahoo.com domain instead of your appropriate address (e.g., yahoo.co.uk or yahoo.fr).

The message was delayed.

Most messages are delivered within a few minutes, but messages can sometimes be delayed while in transit due to problems on the sender's mail server, heavy Internet traffic, or routing problems. (On rare occasions, delays can last for several hours or more.)

The sender's address is blocked.

The Blocked Addresses feature in Yahoo! Mail allows you to create a list of addresses that you don't want to receive mail from. Mail coming in from one of these senders will neither arrive nor bounce, but will simply be discarded. Did you block this sender's address? Check your Blocked Addresses list by clicking "Options" in the upper-right corner of the page. Under "Spam," click "Block Addresses." Here you'll see a list of any addresses you have blocked.

You've enabled mail forwarding.

Are you a Mail Plus user? Good choice! Check to see if you set your mail to be forwarded to another email address. Click "Options" in the upper-right corner of the page. Under "Management," click "POP Access and Forwarding." If there's a dot in the box beside "Forwarding," you're forwarding messages to a different address. Click to remove the dot.

You've set up filters.

You might have set up filters which caused the message to be sent to the Trash folder or to another folder within your Yahoo! Mail account. To check, click "Options" in the upper-right corner of your Yahoo! Mail page. Under "Management," click "Filters." Are there any filters listed? If so, ensure they're not set to prevent receiving emails from this sender.

Note: Mail in your Trash folder can be deleted at any time. Check your filters to ensure that all your mail isn't going straight into trash!

Other possibilities.

Occasionally, interruptions or disruptions in email transmissions over the Internet will render a message undeliverable. While this is very rare, it does happen. Unfortunately, aside from waiting, there's no way to know whether a message has been delayed or whether it has been rendered undeliverable. If a sender can re-send it, have them do that.

No matter what the cause, the best solution is to ask the sender to re-send the message. Also, check your mail again to see if you've received their message.