Why isn’t my iPhone SE Gen 2 automatically deleting junk mail after 30 days anymore?

Not an urgent issue since I don’t get much junk mail, but still perplexing. My Junk Mail folder used to automatically trash an email that had been in it for 30 days, which is what Apple support says should happen. But I now have an email in there that is 37 days old. I could delete it manually, but I’d like to have a real fix. I checked all the options in iCloud mail and saw none that would address this. While I doubt this is a relevant point, I note that the email in question seems to be in Japanese characters, while I am in the US and speak English. I power down my phone most nights. Thanks.