I had this same problem with my zoho mail account. It started when I changed my email password on the computer....Long story short I have been going crazy for a few days. I could receive mail, but couldn't send anything from that account! (Fortunately I have two other accounts which are a different server - gmail.) I turned my iPad2 off then on again...I did a sync with iTunes...I deleted the account and then added it back...Still it would not send..Just receive!
I did finally get it fixed, but it took about an hour poking around and looking for help here.
There were several problems:
1. Somehow the server port numbers were incorrect. So when I added the account back in, I found that the "incoming server port" was not correct and fixed it. But I didn't see how to check the "outgoing server port." - somehow in the setting up process, that just wasn't exposed.
2. Eventually I found the "outgoing server port" here: - Go to Settings - General - Mail - Account. Then tap on the Account you need to fix. Check the information there to be sure it is correct.
THEN: tap on the white bar just below the word "Outgoing mail Server"
That takes you to "SMTP"
You will see a primary server, and "other SMTP servers"
Somehow I had 3 there that were the same account server name (zoho) ..all with the wrong port number!
But even after fixing each one, I still couldn't send mail. This led to problem number 3:
3. Apparently having 3 of the same account was a problem. After I deleted all three of the accounts, then tapped on "Add Server" and entered the information back in again. Bingo, I could send mail!!
I don't know why, but now my "Primary Server" says "Not configured - off"
And all the "Other" servers say "off" as well.
But it's working so I am going to leave it as it is.
I hope some of this is helpful.