My situation is exactly the same - SMEserver 7.51 (yes I know I need to upgrade) been running for years and I get the same spf error message back just starting Wednesday afternoon(5/21). I also tried to clear some space, but that also did not fix the issue. The only other change I know of is that my server is on a static ip on Verizon fios and they had replaced/added some bandwidth to my area that results in an even faster connection for me. All of my server functions work.
My email works as long as it is the smtp sending out, and it can receive from the same "@myemail.org" addresses that use my smtp. But any incoming email from another smtp gets this hard bounce. Like another question posted, I would appreciate any other pointers.
