I don’t know.
- I don’t need formatting but it doesn’t get in the way either. So I am not bothered by it.
- Also pdf and especially PDF/A standard is widely used for archiving and compliance regulation concerning archival and preservation.
- If you want text the same tactic goes: just export in bulk to txt instead of pdf
My main point is: Why would you want a mail specific stack of hosting, storage, indexing and frontends? If it’s all plain text anyway so the regular storage solutions for files come a long way.
There is an entire industry (which has its own disadvantages) to get communication artefacts out of those systems and put it in document management systems or other forms of file based archival.
Must admit, those fields are precisely the ones I use in my filenaming convention. Other DMS put that in their databases but alas that’s just trading one stack for another.
Other ones put it in XMP metadata of the pdf themselves. But I guess the work involved would be similar.