since upgrading software, I can receive but not send email from my phone. have tried deleting account and then adding it again. No luck.

call youremail provider and ask them the settings for the outgoing email server

I have this problem too and did this but the outgoing email server details were correct, so there's something else going on. I think it means a visit to the Apple Store......

Since receiving my 5s iPhone, I can send and receive e-mail on one account. My other account will receive e-mail but cannot send any. I was told to delete the account and add it again. I have done that many times. The username and password work on all our other devices. I get an error message when I go to send an e-mail which says either the username or the password is incorrect. I was told to call my e-mail provider. They said they would fix my iPhone for $49. I said, "No thank you." I have spent many hours on this.

I had the same problem, see my reply above. I got it fixed! Instead of deleting the account and putting it in again, which doesn't work, go to the account: Settings, then Mail, Contacts, Calendars, then go to the account that you are having problems with and scroll down to Password. Delete it and put the correct password in again. I was very pleased to get help with this and saved $49 or a 75 mile trip to an Apple Store.