Q: I'm getting a message that I've exceeded my sending limit and the message goes into Outbox. Only using icloud . Any ideas?

Have you exceeded your sending limits. iCloud has several safeguards to ensure that only iCloud members can send messages using the iCloud outgoing mail server. Among these safeguards are reasonable limitations on:

• The total number of messages you can send each day (200 messages)
• The number of recipients to whom you can send each day (1000 recipients)
• The maximum number of recipients per message (100 recipients)
• The size of incoming and outgoing messages (20 MB)

Check that out, helped someone else, see if it works for you...

https://discussions.apple.com/message/22532900