Trouble with Email and Attachments

Hello, Iam using Outlook 2011 with 10.7. In many cases it is taking forever for emails to download or open -- sometimes they never want to open. It appears to be a problem only with emails with attachments. If I am able to open the email, the attachment won't open. It appears to be a server conflict. The only way I can view an attachment is by forwarding the email to my Yahoo account, then it opens without a problem. Help!!