iCloud outgoing email stuck in outbox

I have a 32 GB, WiFi-only, iPad 2. I have multiple email accounts on the iPad, but lately my iCloud email account refuses to send emails. The email messages essentially get stuck in the outbox. The pinwheel spins for a time before a red exclamation point shows up. When I click on the exclamation point, I receive a message indicating "the connection to the outgoing server 'p05-smtp.mail.me.com' failed. Additional outgoing mail servers can be configured in Settings>Mail, Contacts, Calendars." None of the other accounts on my iPad experience this problem. Meaning, I can send and retrieve messages from the other accounts without fail. Plus, my iCloud account receives email messages just fine. The problem only seems to relate to messages that I send via my iCloud account. I've seen a few posts about this problem on this and other sites, but none seem to identify a solution to this issue. Any help would be greatly appreciated.