Internal error with SMTP server

I have 2 separate Cox email accounts set up in Outlook 2013. The primary email associated with my Cox account receives email just fine, but I get an error message when sending:

"Your outgoing (SMTP) e-mail server has reported an internal error.  If you continue to receive this message, contact your server administrator or Internet Service Provider (ISP).  The server responded: 554 eastrmimpo110.cox.net too many bad commands fr"

I am using the following settings for the SMTP server:

server name: smtp.cox.net
Box checked for outgoing server requires authentication (use same settings as incoming mail server)
outgoing server 465, SSL

I have a secondary Cox email account set up in Outlook at the default account to send.  I use the same exact server settings as above and can send with no errors.

I need to be able to send from either account, so please advise what the issue could be.