I use Thunderbird on my Mac M3 laptop and the Apple native tool on my iPhone. Until recently deleting or moving email on my iPhone didn’t same on my laptop, and vice versa. Starting several weeks ago I realized that I could delete email on my laptop but the copy was not deleted on my iPhone. The same is true when deleting on my iPhone — the email remains in my inbox on Thunderbird. I use two mail accounts: Gmail and an institutional (university) MS Outlook 365 account. The same behavior occurs for both. And both used to sync up in the past.