Invalid internal recipient   This MailTip is displayed if the sender adds a recipient that may appear to be exist in the organization but doesn't. For example, a sender may add a nonexistent recipient to a message if the recipient is in the sender's AutoComplete cache or in the sender's Contacts folder.

Note   This MailTip is supported by Outlook 2010 only.

• The e-mail message cannot be delivered to <recipient> because the e-mail address is no longer valid.
  

Mailbox is full   This MailTip is displayed if the sender adds a recipient whose mailbox has exceeded the Prohibit send receive quota restriction for the mailbox.

• This message can't be delivered to <recipient> because their mailbox is full.
  
• This message can't be delivered to <recipient 1> and <recipient 2> because their mailboxes are full.
  
• This message can't be delivered to <number> recipients because their mailboxes are full.
  

Automatic Replies   This MailTip is displayed if the sender adds a recipient who has enabled Automatic Replies.

The MailTip indicates the recipient has Automatic Replies turned on and also displays the first 250 characters of the automatic reply configured by the recipient.

• <recipient> Automatic reply: <automatic reply configured by the recipient>
  
• <number> recipients are sending automatic replies.
  

Restricted recipient   This MailTip is displayed if the sender adds a recipient who the sender is prohibited from sending messages to.

The MailTip indicates the restricted recipient, and gives the sender the option to remove the recipient from the message. It also clearly informs the sender that the message won't be delivered if it's sent.

• You don't have permission to send to <recipient>.
  
• You don't have permission to send to <recipient 1> and <recipient 2>.
  
• You don't have permission to send to <number> of the recipients.
  

External recipients   This MailTip is displayed if the sender adds an external recipient or adds a distribution group that contains external recipients. The sender can decide if the message wording, tone, or content is appropriate for external recipients.

By default, this MailTip is disabled. You can enable it using the MailTipsExternalRecipientsTipsEnabled parameter on the Set-OrganizationConfig cmdlet. See Configure the external recipients and large audience MailTips.

• The following recipient is outside your organization: <e-mail address>
  

Large audience   This MailTip is displayed if the sender adds a distribution group that has many members. The MailTip indicates the number of recipients in the distribution group. A distribution group that is a member of a distribution group counts as one recipient.

By default, this MailTip is displayed for distribution groups that have more than 25 members. You can configure the threshold using the MailTipsLargeAudienceThreshold parameter on the Set-OrganizationConfig cmdlet. See Configure the external recipients and large audience MailTips.

• This message will be sent to <number> recipients.
  
• <distribution group> contains <number> recipients.
  

Moderated recipient   This MailTip is displayed if the sender adds a moderated recipient who requires the approval of a moderator before the message is available to the recipient. This MailTip isn't displayed in the following circumstances:

• The sender is the moderator of the recipient.
  
• The sender is defined in the recipient's RejectMessagesFrom list or isn't defined in the recipient's AcceptMessagesOnlyFrom list.
  

• Messages sent to <recipient> are moderated. They may be rejected or delayed.
  
• Messages sent to <recipient 1> and <recipient 2> are moderated. They may be rejected or delayed.
  
• Messages sent to <number> of the recipients will be moderated. They may be rejected or delayed.
  

Reply All on Bcc   This MailTip is displayed if the sender selects Reply All to a message they received as a Bcc recipient. This action reveals the fact that the sender had received the message to the rest of the original recipients in the To and Cc fields. In almost all cases, this is undesirable.

Note   This MailTip is supported by Outlook Web App only.

• Your address was hidden when this message was sent. If you Reply All, everyone will know you received it.
  

Oversized message   This MailTip is displayed if the message size is larger than the message size limits in your organization.

Note   This MailTip isn't supported by Outlook Web App.

• The attachment size exceeds the allowable limit.