failed: Invalid cross-device link

Hi.

I mount ~/Maildir/new via s3fs

s3fs mybucket /home/kes/Maildir/new -f -o use_cache=/tmp/S3 -o noatime -o endpoint=eu-west-1 -o profile=mail -o allow_other -o uid=1000,gid=1000

I configure dovecot:

maildir_copy_with_hardlinks = no

Nov 15 19:30:48 work dovecot: imap(kes): Error: rename(/home/kes/Maildir/new/ddd3, /home/kes/Maildir/cur/ddd3:2,) failed: Invalid cross-device link

Tell me please, why I still get this error and how to fix it?