When you hit \u201cCheck Name\u201d, Outlook does a user lookup to resolve the input username to a mailbox. Outlook will first attempt to use the users local credentials to authenticate, then any cached credentials (Windows Credential Manager), finally, if no credential entries authenticate then Outlook will prompt the user for credentials. <\/p>\n
If a user does not receive the credential prompt and receives the error \u201cAction cannot be completed\u201d a quick fix is to go to More Settings, Security, and then enable the checkbox to \u201cAlways prompt for logon credentials.\u201d <\/p>\n When user\u2019s select \u201cRemember my credentials\u201d Outlook then creates a cached credential for windows in the credential manager <\/p>\n Normally, this works as expected.. the next time Outlook launches it will try the cached credential which would authenticate. <\/p>\n But imagine if you were trying to add a second mailbox to the users profile (Let\u2019s say the CEO has two mailboxes for \u2018two different companies\u2019) .. how is Outlook to know that the cached credential for servertest@louie.exchangedefender.com<\/a> on \u201ccas.louie.exchangedefender.com\u201d isn\u2019t for the second mailbox (Let\u2019s say servertest2@louie.exchangedefender.com<\/a>)? The answer is..Outlook won\u2019t be able to tell the difference.. The server will respond to Outlook with the message \u201cAccess denied\u201d because the cached credentials for mailbox1 does not have permission to access mailbox2 (Think of it as trying to access mailbox2 via OWA, but using the credentials for mailbox1) and then receives the error \u201cAction cannot be completed. Name cannot be resolved\u201d when trying to resolve the mailbox name for mailbox2..the key point is that this failure will instantly occur and there will be no prompt for the user to provide credentials because the error \u201cAccess denied\u201d mean \u201cYou have a valid account here, but it does not have access to this resource\u201d. <\/p>\n Now let us imagine the inverse where a user gets prompted for credentials every time no matter how many times they select \u201cRemember my credentials\u201d or if they follow our help article \u201cMy Windows OS won\u2019t hold the Outlook authentication info!<\/a>\u201d and manually add \u201c*.exchangedefender.com\u201d to the credential manager.. This is because Outlook is passing off a valid \u201cAccount\u201d that has access to the resource (Mailbox), however, the credentials being passed off are incorrect. If Outlook tries to authenticate with invalid credentials the server will respond back with \u201cInvalid credentials\u201d..notice how this isn\u2019t the same error as \u201cAccess Denied\u201d which is why Outlook will then prompt the user for credentials. To solve this we tell users to delete all references to any exchangedefender servers in credential manager and then manually add the credentials (following the above blog post) and then adding *.exchangedefender.com to the \u201cLocal Intranet\u201d zone in Internet Explorer. This should allow Outlook to trust our servers to hand off the credentials. <\/p>\n Finally, the last common scenario for the two failures (either no credential prompt or reoccurring credential prompts) is if the local users login name matches a username on the server. Remember, Outlook will first try the local logged on users credentials. Now imagine if my local login name was servertest@louie.exchangedefender.com<\/a>… then any time I attempted to add an Outlook profile I would either instantly authenticate or I would always get the credential prompt. Can you guess why? Its because either the local users credentials (Either their local computer user name or an active directory account) match the servers credentials. <\/p>\n Active Directory:<\/strong> <\/p>\n \u00b7 Username: servertest@louie.exchangedefender.com<\/a> <\/p>\n \u00b7 NT Username: servertest <\/p>\n \u00b7 Password: 123456 <\/p>\n![\"clip_image002\"](\"http:\/\/www.exchangedefender.com\/blog\/media\/Action-Cannot-Be-Completed.-Name-Cannot_D2B0\/clip_image002.jpg\" "\\"clip_image002\\"")
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