I'm not sure those capitals make a difference, but...

When you look at your sent items, does it show that you used the correct address?

If not, are you letting Firefox autocomplete the address? To delete an autocomplete suggestion that appears below a form field, you can use the keyboard: arrow down and press the Delete key to remove it.

Thanks for your suggestions, but not the answer. Someone told me that the caps matter on AOL. I did not use auto-suggest and typed it in with the correct caps. Postmaster showed the address with all lower case.

It sounds like a problem on AOL's end if you sent the message with the correct address. Or a problem with your own email service provider.

What is the reason given in AOL's message for nondelivery? Often there will be a text description, or a 3-digit code indicating the reason it couldn't be delivered, or both.

"This is an automatically generated Delivery Status Notification.

Delivery to the following recipients failed.

      [email protected]"

The address I use is [email protected]

Seems as though they really didn't give you any detail. Usually it will provide a cause, such as, mailbox full, unrecognized address, spam filter, etc.

So no remedy?

I don't have a remedy because I don't know why the message isn't going through.

Can your mail service provide any additional insight?

Does it work in Internet Explorer?

This still sounds weird to me that an email address only works with the proper case as that would cause severe problems with receiving e-mail if this would happen there as well.

Clear the cache and cookies only from websites that cause problems.

"Clear the Cache":

• Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > Cookies: "Show Cookies"

Use these steps to remove saved (form) data from a drop-down list:

1. click the (empty) input field on the web page to open the drop-down list
2. highlight an entry in the drop-down list
3. press the Delete key (on Mac: Shift+Delete) to remove it.

You can remove all data stored in Firefox from a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History > Show All History" or "View > Sidebar > History") or via the about:permissions page.

Using "Forget About This Site" will remove all data stored in Firefox from that domain like bookmarks, cookies, passwords, cache, history, and exceptions, so be cautious and if you have a password or other data from that domain that you do not want to lose then make sure to backup this data or make a note.

You can't recover from this 'forget' unless you have a backup of the involved files.

It doesn't have any lasting effect, so if you revisit such a 'forgotten' website then data from that website will be saved once again.

After I chose "Clear now" for the web content, the full window wasn't showing for me to click Save, so I don't know if it took. I tried to send another message to that AOL email address and it was rejected again.

Under "Privacy" there was no cookies option for me to choose "Show cookies".

I don't know what you mean about the drop-down list in the input field on a web page.

Thanks to you both for helping me so much with this.

Thanks so much for all your help! No, using Explorer didn't help. In fact, I couldn't close Explorer and had to End the program! Also, my computer is running REALLY slowly. Amazon had a tab I'd have to close every time I'd get on line, and now it says I don't have any email filtering protection. I use Avast basic antivirus.

I don't know how to get help from MSN Hotmail.

To see all History and Cookie settings, choose:

• Tools > Options > Privacy > Firefox will: "Use custom settings for history"

• https://support.mozilla.org/kb/Options+window+-+Privacy+panel

The text about the drop-down list is about using saved form data to fill entries in a form on a web page.

• https://support.mozilla.org/kb/Form+autocomplete

Hotmail, now migrated to live.com under the Outlook brand, is supported by Microsoft. Perhaps they can help figure out why the messages aren't going through? This is their general help page on that:

http://windows.microsoft.com/en-us/outlook/delivery-failed

There are more support options toward the bottom of that page.