I get the error message Mailbox unavailable when I try to scan to email.

Hello, Joe -

You received a phishing email. Read about it here:
https://www.onlinethreatalerts.com/article/2017/5/6/beware-of-we-are-closing-all-old-version-of-yahoo-mailbox-new-mail-upgrade-phishing-scam/

DO NOT tap or click on any links in that email message!

Delete it and run your antivirus protection as a scan, just in case some malware was installed on your computer when you opened the phishing message.

Best wishes.

550 generally means the mailbox is unavailable. Make sure you typed the address in correctly. If you're just hitting reply, the person who sent the original message may have misconfigured their email client with the wrong "reply to" address.

- Stop the Microsoft Exchange Search Indexer service. Run Stop-Service MSExchangeSearch if you are into Shell.
- Browse to where the database files are located on the disk. Along with the database file, you will see a folder with "CatalogData-random string" as its name. Delete this folder, which stores the corrupt index.
- Restart the Microsoft Exchange Search Indexer service. Run Start-Service MSExchangeSearch if you are into Shell.
- Give it a minute and a new folder will be created and a new index will be built.
If you are still experiencing the issue after applying this fix you can try Exchange Server Repair Toolbox https://www.repairtoolbox.com/exchangeserverrepair.html

I would say try moving users mailbox to see if that would help if not then no other option than to Restore from backup.

If doesn't help, look here: http://www.filerepairforum.com/forum/microsoft/microsoft-aa/exchange-server/734-repair-exchange-priv1-pub1-edb

Or: Exchange Server Repair Kit is an absolute must-have for any software development professional working with MS SQL databases.
For more information: http://www.exchangeserver.repair/

Maybe, all you needed was to configure the "outgoing" mail-server, so that the printer could send to that server, and that server would send the message to your mailbox.

If you are unable to restore emails from outlook it might be corrupt. You can try Data Recovery Pro - Recover Deleted Files and Emails .This completely scans the damaged mailbox file and revives the lost emails. & recovers your accidentally deleted messages that have also been removed from the "Deleted Items" folder
Go to
Hope it Helps
Thanks

550 error code means the mailbox of the recipient your sending it to either is unavailable(server it is on is down) or the mailbox doesn't exist.

check your trash folder in yahoo mail for deleted emails How to Retrieve Email When Deleted From Trash
When emails are deleted from a folder they usually go to the "Trash Bin" and can be restored to their original location. Emails erased from "Trash" are considered permanently deleted by all email programs. Unfortunately, there are neither general nor easy ways to retrieve emails deleted permanently. The usual strategy is to relay on a backup of the mailbox. Some web based mail services allow you to successfully retrieve deleted mailbox content because, for limited time, they keep backups. The Yahoo Mail can do a rollback of a mailbox to the time specified by the user.
jQuery('.intro .thumbnail').each(function(i,e){ jQuery(e).find('img').one('error',function(){ jQuery(e).remove(); }); }); Difficulty: Moderately Easy Instructions

1. Step 1 Open the web browser and navigate to Yahoo Mail.
   
2. Step 2 Login to the Yahoo account by providing Yahoo ID/password information.
   
3. Step 3 Decide on the account rollback time that should be about 1 hour earlier than the incident time . Example: if a email was deleted from Trash at 5:15 p.m. choose the mailbox reset time for 4:15 p.m.
   
4. Step 4 Save, print or forward to another account all messages received after the time selected in the step 3.
   
5. Step 5 Open another instance of the web browser and navigate to the Yahoo! Mail Restore Help Form.
   
6. Step 6 jQuery(document).ready(function(){ jQuery('#jsArticleStep6 span.image a:first').attr('href','http://i.ehow.com/images/a04/qt/n7/retrieve-email-deleted-trash-1.6-800X800.jpg'); }); Under "Mailbox recovery information" select Month, date and time (15-minute increments) chosen in the step 3. Make sure to fill out the time zone field and specify an alternative email account to receive a confirmation email.
   
7. Step 7 Click "Submit" on the bottom of the page.
   
8. Step 8 Continue monitoring the mailbox and keep backing up all incoming messages (see step 4).
   
9. Step 9 The confirmation email from Yahoo mail customer care usually arrives in 6 to 8 hours and the mailbox should be restored as it was on or around the time entered in the step 6.
   

Try this if it doesn't work tell me and I will continue troubleshooting

After you type the address to Microsoft Outlook Web Access (OWA) on an Exchange 2003 computer, you may receive the following error message on your browser before you receive the OWA log on prompt: 503 Service Unavailable
This problem occurs if the Davex.dll file cannot communicate with either a mailbox store or a public folder store.
Make Sure That All the Services Are Running
The "503 Service Unavailable" error message may occur if the Exchange 2003 services are not running, particularly if the system attendant and the information store are not running. To view the services and make sure that all the services are running!!

Ryan Frame
Creative Energy Associates Technical Center