Yes, Sortd requires IMAP to be enabled on your Google account and in particular on your 'Inbox' and 'All Mail' labels. IMAP is enabled by default, but to verify go to Settings -> "Forwarding and POP/IMAP" from within Gmail and ensure that "Enable IMAP" is selected. You can also confirm that IMAP is enabled on your labels by going to Settings -> Labels and confirming that the "Show in IMAP" box is ticked next to the "Inbox" and "All Mail" labels.