I think I implicitly knew this, but as I've just released a package (to be announced soon) that actually has multiple authors, I found out first hand that PyPI rejects uploads where the author-email field isn't a completely valid email address, and that there is no support for multiple author emails. As it turns out, you can kludge this into your pyproject.toml or setup.py file. flit for example separates multiple emails with a newline, but you could also separate them with commas. You don't notice the problem until PyPI rejects the upload (with a 400 IIRC). I filed this issue with flit: https://github.com/takluyver/flit/issues/153 It looks like Thomas agrees that at least flit will eventually validate its fields so you error early. It was a bit of a PITA to do my upload because I didn't notice the problem until after I'd tagged the repo. Multiple package authors doesn't seem like that fringe of a use case; are there any plans, documents, PEPs, musings, grumbles about supporting multiple package authors explicitly? Cheers, -Barry