postfix/postdrop warning: uid=48: Illegal seek postfix/sendmail: fatal: (48): queue file write error

If you got the error. And you are not able to send large size/ mail attachment from postfix please do above config.

postfix/postdrop warning: uid=48: Illegal seek
postfix/sendmail: fatal: (48): queue file write error

Edit the postfix mailserver file:
vi /etc/postfix/main.cf 
Change/Add this option to  send large file size.

message_size_limit = 100000000
mailbox_size_limit = 800000000