Where is my email?

Can you include a bit more info? How are you checking your email? If a client, POP3 or IMAP? And what do you mean "didn't delete". Did you delete other emails? 

Already opened email w/ airline confirmation info from last week.  We did not delete & I have not cleaned up mail in the interim.  Cannot find w/ Outlook or Cox webmail.

So you use Outlook. How is it configured? POP or IMAP? If POP, do you have it set to leave a copy on the server? For instructions on finding out, see here.

Also, have you checked your trash or other folders in outlook? Maybe do a search for the message?

IMAP.  (clarification: Office Outlook, not OUTLOOK)  Yes I checked trash & have not emptied it in the interim. 

What is the relevance of server configuration if a received/opened/undeleted mail has vanished?

bikesomnia said:

What is the relevance of server configuration if a received/opened/undeleted mail has vanished?

Very relevant ... if you have any device configured as POP and not configured to leave a copy on the server, as soon as you open e-mail on that device it will download a copy and delete the original from the server.  The only copy left will be on the client configured as POP.  When the POP client deletes it from the server it will also be deleted from all IMAP clients.  So, the server configuration on all clients accessing your e-mail is relevant.  If you access your e-mail via your phone, tablet, etc., check there too.

I am only using my desktop for access.  I did not delete it.  Are you saying the sender may have POP configuration & deleted it?

bikesomnia said:
 Are you saying the sender may have POP configuration & deleted it?

No. The sender is not involved. Think of the email server like your local post office. Outlook is like your mailbox infront of your house, you can configure it to copy all the mail at the post office, or download and keep it. Each device you set up (desktop, laptop, phone) is like a different mail box at your house, and each can(but shouldn't) be set to get the mail differently.

So if you use IMAP on your desktop, either the desktop or something else told the server to move or delete the message. My guess is the email is either on another device (phone?) you have set up for email, or it's hidden in some folder. Try searching any device you ever configured with Cox email.

If all else fails, can the sender re-send? 

I only use desktop to access that email account.  I have checked all mail folders.  No changes have been made.   My conclusion points to a Cox mail server fail.  Again.  I am really tired of their poor mail service.

bikesomnia said:
My conclusion points to a Cox mail server fail.

Possibly, but how? It's weird it would only effect 1 email. Have you lost other emails before? 

bikesomnia said:
 I am really tired of their poor mail service.

Personally, I don't use it or any ISP email. Doesn't make sense to me to tie something so cructial so something that may change. If nothing else, you can set Cox to forward all you email to another provider that way you always have a copy in the cloud. 

Thanks, good advice.

Is the email SUPER important? Cox does have a way to recover email from tape backup, but it's a paperwork nightmare. I have seen it used to recover entire inboxes, but never 1 email. I think it might just be easier to get the sender to re-send, thats why I didn't mention it.