Keep in mind:
For that you need also a setting for a special folder "Archive" in sogo.conf and in the users email folder settings, like the existing ones for "INBOX", "Drafts", "Sent", "Spam" and "Trash".

I get here to request support of Archive folder :), but found that people already request a button for this which can't works without support of folder standard, so I upvote this +. Good idea.

Same for is: upvote this request. With the amount of e-mail receiving nowadays, an kaveling and archiving feature is almost a must be :- )

Hi there! Thank you for your great mail client. I just registered to upvote this feature. This is the first web client where I haven't seen the archive button. It would be awesome to have it. Thank you!

Thanks for reporting, this is not currently in our roadmap however we will discuss internally about this

Sebastien