Heads-up: if you have a pypi.org or test.pypi.org account, please verify your email address:
We have a problem with a bit of our data, namely that due to historical reasons we have a fair amount of users in the database that do not have a verified primary email address. The side effect of this is that we're currently sending emails to email addresses that we have not had verified. This is a bad situation to be in, because in order to keep our bounce/spam rate low, we should be confirming all email addresses before sending email to them. In addition the way our bounce handling code works is it un-verifies the email address, which the intent was to stop sending email to it until the user has reverified their email address.
(quoting from Donald Stufft's explanation https://github.com/pypa/warehouse/issues/3632 which goes on to detail the step-by-step plan)
We have over 180,000 user accounts with unverified primary email addresses. Since it's important that we don't send email to unverified addresses, we're gradually adding restrictions on what accounts with unverified primary addresses can do. As of a few days ago, any user whose primary email address is unverified can't upload a file: https://github.com/pypa/warehouse/pull/4292
Please forward to other PyPI users, especially package maintainers.