Long time no technical post; here's a solution to a small but frustrating error I saw today.
I got this while sending a mail with a huge attachment:
postdrop: warning: uid=1000: Illegal seek
sendmail: fatal: amit(1000): queue file write error
Now this is because postfix (according to their man page) defaults to a 10MB file size limit. Though my attachment was much smaller than that, it was blocked. So I'm guessing the manpage and the real default are out of sync. I set the 'message_size_limit' to 15000000 (slightly less than 15MB) in /etc/postfix/main.cf. This worked.
(I use postfix 2.3.3 on Kubuntu.)