setting PRIMARY outgoing Mail Server

You cannot delete a secondary SMTP server if it is the primary server for any account. That's why you can't delete most of them.

You need to edit the primary account to use the correct SMTP server for that account. Tap on the Primary server and change the fields to the correct server. Do this for each email account you have on the phone. After you are done none of the primary servers should be cwmx.com. Then you can delete the redundant ones.

It would be nice if there were a way to change them with a dropdown, but you have an unusual situation; Normally when you set up an account the first time the correct SMTP server gets inserted. I don't see how you got into this situation in the first place. I suspect that when the accounts were created there was no SMTP server defined for them, so the iPhone put in the only one it knew, cwmx.com.

Well, first, you only need one copy of each server. cwmx.com is AT&T's SMTP server, and will only work when you are on cellular data; it will not work over WiFi. So start by deleting all cwmx.com servers except the first. cwmx.com should not have a user ID or password.

When you send mail the iPhone first tries to send using the primary SMTP server. If that fails or times out, it tries the secondary servers in the order listed. cwmx.com is a last resort server; most people don't need it at all; it is only needed if your ISP does not relay mail from outside of its network.

For each mail server that you interact with the Primary SMTP server should be the one for that server. The Primary server should never be cwmx.com. So for the universaljointdesign.com account the primary server should be mail.universaljointdesign.com, and you should enter your user ID and password. The secondary should be cwmx.com, and you should turn off all of the other SMTP servers for that account. Further, if mail.universaljointdesign.com does not require that you be within the site firewall when sending you don't even need cwmx.com enabled.

For the gmail account the SMTP server should be smtp.gmail.com, and that's the only one that needs to be on. You will need to enter your full gmail address as ID and your gmail password. If you have 2 factor authentication enabled for gmail you will have to generate a single use password.

Default Account has nothing to do with SMTP servers. The Default Account is the account that will be used to send email from another app - for example, if you take a photo and choose to send it by email that is the account that will be used. When the email is generated you can select a different account to use if you don't want to use the default account

The default email account will use the selected SMTP server for that account. Selecting a different server than the normal default that requires you to login using a email address and password will send emails that appear to come from the selected email account associated with that SMTP server. BTW, replying to an email sent from a particular email account will use the SMTP server associated account even from the All Inbox.

Go to Setting > Mail, Contacts, Calendars, tap Default Account under mail accounts and select the account you want as the primary/default.

You have to go into each domain, set the primary server for it, then turn off the ones you don't want to use with that domain. If you tap on the name of a server there will be an on/off switch.