Some email addresses are no longer being delivered and are not in the spam folder.

My observation is that the email provider for those recipients is rejecting your email as unsafe. Some email providers, such as Gmail, are very security conscious and prefer to remove possibly unsafe emails immediately with no response. Knowing why it is being done is a project in itself. This happens more frequently with self-hosted email accounts as their settings are often not as secure as those obtained from an email provider.

I misspoke, or perhaps the translation changed the meaning. It's me who isn't receiving emails from certain people (that I used to receive). I discovered that it's only emails from orange.fr that aren't arriving.

This type of problem requires some detective work. My first suggestion is to check your online account, as it may be that your email provider is trashing the messages, or refusing to accept them. If possible, ask someone with an orange account to send a simple message with no attachments and see if it appears on the website. Does that person receive a message that the email was not delivered? Knowing that will give you useful information if you need to discuss with the email provider. This type of problem happens usually when the recipient (you) is using a self-hosted email account. True? If so, please share more information, and someone here may have suggestions on this. Thank you.