Can't Connect to Comcast Email

Trying to connect my simple imap/smtp comcast email to mailspring. I am using

SMTP: 587 STARTTLS (but I also tried SSL/TLS)

These are the recommended settings on Xfinity’s website. I have tried all recomended ports and I get this error

“The SMTP server would not relay a message. You may need to authenticate. (SMTP)”

I know that I am using the right password because I am able to log into web-mail from Xfinity. The IMAP seems to be fine and it lists all of my email folders in the log.

This is the tail end of the mailspring log for the SMTP portion (seeing as IMAP works)

"235 2.7.0 … authentication succeeded
250 2.1.0 sender ok
550 5.1.1 Domain not found (no SOA/NS), check spelling

SASL_PATH: /usr/share/mailspring/resources/app.asar.unpacked

SMTP Last Response Code: 550
SMTP Last Response: 5.1.1 Domain not found (no SOA/NS), check spelling"

Here are the instructions that Xfinity gives

Fixed with newest version of program