People send embarrassing e-mails (or worse) to the wrong recipients. MailTips is designed to make sure your communications are right the first time and to avoid such embarrassing mistakes. Exchange 2010 with Outlook 2010 contain these very helpful tips
If you know that the person you are about to send an e-mail to is out of the office, you probably won't send the e-mail to begin with. This will save you and the recipient both time and mailbox space.
When sending an e-mail to a large number of recipients, such as a distribution list, a MailTip will warn you of the amount of users you are about to send the e-mail to. This will probably make you think twice before sending an e-mail to 300 people asking if they know how to get to the closest GAP store!
MailTips will warn you when you are about to reply-to-all on a message that was BCCed to you. This can often prevent some rather embarrassing situations. After all, BCCed recipients are normally meant to stay invisible to the rest of the recipients.
It basically warns you if any of the recipients you are sending to are external or not.
This MailTip lets you know whether the recipient's mailbox has enough capacity to receive your message.
A warning will be displayed if the message you are composing exceeds size limits set by your Administrator.
MailTips will tell you straight away if you don't have permission to send to a particular mailbox or distribution list.
This MailTip informs you whether the mailbox to which you are about to send an e-mail still exists. In Exchange 2007 and earlier, if you send an e-mail to someone whose mailbox has been disabled or deleted, you'd get a non-delivery report. This MailTip helps prevent that, for example it is particularly useful when trying to send an e-mail to someone who left the company.
These mail tips are available to users even when they are using the OWA.