Interpro has many annotations though, not just domains...
(And I'm wokring on offline sequences which aren't necessarily in Uniprot; or even NCBI.
As for your approach on a database, Wouldn't i make more sense to just search for proteins with "NOT domain:*" ? Your query has proteins with annotated domains right on the first page of results :P)
what is emailed file output? I think, after you blast against a domain database, all those sequences with no hits are considered as sequences without domains. Am I missing something?
I was working then with the HMMER and/or PFAM search results, which are returned as a plaintext email. Yuch.
That said, even with the offline tool, I don't know how to parse the command line output text properly, it just prints it onscreen.