I think this is more an IOS 8 issue but my wife and I have the same problem and also read a few other posts about this today. Outgoing messages fail to send. Problem seems to be with SMTP server and loss or corruption of password. Sometimes I get a prompt to enter SMTP password and other times message just winds up getting stuck in the outbox which one may not always notice. Re-entering the password in the Mail, settings, SMTP usually will correct the problem but not sure for how long. Is anyone else experiencing this problem. You might want to check your Outbox to see if there are any messages in there.