The known mail servers that are used for sending spam are added to so-called grey lists by email providers and intercepted directly by the mail server. To fix it, your Exchange Server administrator must update to the latest Exchange Service Pack.Spam filters recognize spam mails based on typical content such as frequently used links or the tracking pixels that spammers like to use. – If you are using WBA (Outlook Web Access), there is a known bug in Microsoft Exchange Server version 5.5, when the mailbox storage limit was exceeded.

– Edit the culprit email (Actions -> Edit Message), save it back and try to delete it To start the Outlook Safe Mode, simply type outlook.exe /safe in your Start -> Run window or Windows Search panel (for Windows 7 / 8) – Restart Outlook in Safe Mode and try deleting the emails from there. – Empty your Deleted Items mail folder (right click on it and choose “Empty Folder”), then try again to delete emails This action will bypass the Deleted Items folder and it will put the deleted email directly into to dumpster – Hard delete the selected emails: while the emails are highlighted/selected, keep the Shift key pressed and hit the Delete key. If repairing your data file didn’t solve the problem and you are still unable to delete emails, you can also try one of these solutions: Outlook Email Delete Command Does Not Work – Other Solutions Unfortunately, Microsoft removed the Inbox Repair tool from Outlook 2010. If you are using Outlook 2003 or 2007, you can check it for errors using the Outlook Detect & Repair / Diagnostics tool available from the Outlook Help menu. If you are unable to delete only some emails (while others get deleted just fine), then your Outlook data file might be corrupted. If you are unable to delete emails from a given Outlook folder (not just certain emails), most likely that folder is locked because it is being used by a 3rd party application (for example, it may be scanned by an anti-virus program). This article describes various solutions to this problem. Sometimes, emails can get stuck in your Inbox, Outlook or Sent Items folder and you are unable to move or delete them, while Outlook reports an “unknown error”.

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