Postfix error 452 Insufficient system storage?

Question

Mail server

Good day everyone!
Something bad happened, Postfix 452 Insufficient system storage mail server error
Tell me what exactly to delete to free up space.
Thanks
-bash-4.1# df -hi
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/md2 116M 1.7M 114M 2% /
tmpfs 4.0M 221 4.0M 1% /dev/shm
/dev/md1 128K 63 128K 1% /boot
-bash-4.1# sudo service postfix restart
Shutting down postfix: [ OK ]
Starting postfix: [ OK ]
-bash-4.1# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md2 1.8T 1.8T 0 100% /
tmpfs 16G 4.0K 16G 1% /dev/shm
/dev/md1 496M 119M 353M 26% /boot
-bash-4.1#

Answer 1

How to delete old emails in Postfix (CentOS)?, SSH, SFTP access available