> However, I have yet to find an email provider that mimics Gmail's tagging system
IMAP does support keywords, which are basically tags. Probably some good IMAP-Client supports this?
There is also JMAP as a modern alternative to IMAP in development. Fastmail released a beta-interface for this, which also includes tag-support AFAIK.
And finally, Outlook surprisingly seems to support tagging, but they call it categories(?). It's not obvious at first if you only know traditional categories.
IMAP does support keywords, which are basically tags. Probably some good IMAP-Client supports this?
There is also JMAP as a modern alternative to IMAP in development. Fastmail released a beta-interface for this, which also includes tag-support AFAIK.
And finally, Outlook surprisingly seems to support tagging, but they call it categories(?). It's not obvious at first if you only know traditional categories.