Office 365 Admin Microsoft 365 Business Last updated 2015-10-23 This topic can help you fix email problems that are associated with error codes 550 5.1.1 through 5.1.20 if you see this in a non-delivery report (NDR). Mail flow problems can be frustrating, but we have solutions you can try in order to get your message sent. I sent a message and got error code 5.1.x in an NDR. What can I do to fix this?

Here are 5 different solutions you can try.You might not need to try all of them. If the steps here don’t help you to successfully send the email, then contact your email administrator and refer them to the section of this topic so they can help you. Solution 1: Make sure the recipient's email address is correct This is the most common issue that causes 5.1.x errors. Check for correct spelling. If you change something, send the email again.

Jan 02, 2011  All of a sudden when I click on the [Gmail]/All Mail or [Gmail]/Sent Mail folders I continue to receive Error: 1025 messages. These specify. Error: Unknown Mailbox: [Gmail]/All Mail (Failure) Explanation: Mail could not be received at this time. Account name: 'Gmail' Error: 1025 OR Error: Unknown Mailbox: [Gmail]/Sent Mail (Failure). Office 2016 for Mac is available for Office 365 and Volume Licensing customers. The new versions of Word, Excel, PowerPoint, Outlook and OneNote provide the best of both worlds for Mac users: the familiar Office experience paired with the best of Mac.

Solution 2: Remove the recipient's email address from the auto-complete list Remove the recipient’s email address from the list of suggested names in the auto-complete list, then type it again before trying to send the email. The auto-complete list is a list of suggested names that shows up in your email program when it finds a name that matches what you have typed on the To line. If you need more detail about this, see. • Create a new email message.

• In the To field, start typing the recipient's name or email address until the recipient appears in the drop-down list. • Use the Down Arrow and Up Arrow keys to select the recipient, and then press the Delete key. • Type the recipient’s complete address and then send your message. Solution 3: Make sure the recipient doesn't have an email message forwarding rule in place Did you send the original message to exactly the same recipient address that is shown in the NDR? You can verify this by comparing the address provided in the NDR with the address shown in the original message that is in your Sent folder. If the addresses don't match, contact the person you sent the original message to and ask them if they have an email rule to forward messages and ask if they know it's working correctly.

It worked when I dragged and dropped files from my PC but I'm trying to save some files from my Mac onto it and it's not letting me. When I drag the file over the passport icon it has that stop symbol, the one that's a circle with a slash through it. Not sure if I make sense or not, but this is important. It won't let me back up any of the work I do at home on my mac, so everything is saved to my drive only. My external is a Western Digital My Passport Ultra. How do I customize these passport ultras so they work with mac too? I heard I need to do something along those lines. Hi, I have a MacBook Air and my Passport won’t let me add new files to it. I’ve never had this problem before; I can open the files I have on the Drive, but cannot alter them. I used to have a PC and used the drive for that as well. I wish to copy files from my mac to the drive, it wont allow me. But when I open and copy files from the drive to the mac it works. How do I fix this without formatting the drive? Will setting up the time machine of my mac erase the contents on the drive? A few years ago I bought a Mac. I plugged the Passport into my Mac and it would not let me add or change anything on the Passport, but I could see the files.

Their rule could have tried to send a copy of your message to a bad email address. If the person does have such a rule, they will have to either correct the email address or remove the rule in order to prevent NDR 5.1.x errors.