Cannot send Spectrum emails on Comcast internet

I think I am seeing this issue on this forum but I don't understand the answer/what to do about it.  I can receive but not send Spectrum emails on my Xfinity/Comcast internet.  The error I see in Outlook is an IP or DNS error.  The IP address I checked using ARIN whois is assigned to Comcast in Naples Florida - this looks correct.  The DNS locally is set to 75.75.75.75 DHCPv4.  I'm lost, please help!