I recently logged into our administrator account and was notified we needed to update SPF records for our domain in order to ensure emails were delivered. I called and GoDaddy talked me through adding the TXT record you recommended. The GoDaddy representative did not recommend deleting the TXT files that were there, as he said they were related to GoDaddy's servers. However, once the new record took effect, I am now not able to send any emails. 

I now get the error message "554 5.1.8 Sender Address Blocked" whenever I try to send emails. My other coworkers do not appear to be having this problem, even though we are all using the same email server.

In order to try to repair the problem, I have deleted the new TXT record and am hoping once it is processed and no longer listed on the domain, the problem will go away, but I don't know. Please advise if you have any insights.