Some research into the ECCN codes turns up the following link https://www.bis.doc.gov/index.php/licensing/commerce-control-list-classification/export-control-classification-number-eccn
From that I gather that 5Dxxx should the categories (5: Telecommunications and Information security, D: Software).
As for the numbers, this https://www.bis.doc.gov/index.php/component/docman/?task=doc_download&gid=2337 seems to be a good place to look for further information.
Reading that I think 5D992 should be a good ECCN, but I can not say for sure in your specific case. Skim the document and notes through and see what applies best.
As of ENC or MMKT.
License Exception ENC authorizes certain exports, reexports, and transfers (in-country) of items described in paragraph (a) of this section for the internal “development” or “production” of new products by 'private sector end users,' wherever located, that are headquartered in a country listed in supplement no.
While MMKT
is Mass MarKeT as far as I've concluded. https://www.federalregister.gov/documents/2010/06/25/2010-15072/encryption-export-controls-revision-of-license-exception-enc-and-mass-market-eligibility-submission
All in all, MMKT should probably be good if you're not yanking with the SSL modules or do anything out of the ordinary.