Can't get sendmail to work from crontab job.

[Calum433]

I have a job run by crontab which produces a log file.
I want the job to email me the log file on completion.
sendmail works and if at the prompt I enter

/usr/sbin/sendmail -t < logfile

I get the mail ok.

The crontab job works as follows.

cat mailheader > logfile

(where mailheader contains
To:mymail@account.com
From:batchjob
Subject:batch job log
Body

Then

runjob >> logfile (where runjob is the batch job)

and finally

/usr/sbin/sendmail -t < logfile

When I view the resulting logfile it looks fine.
If at the prompt I execute

/usr/sbin/sendmail -t < logfile

I receive it ok.
However, from the crontab job, nothing.
Help.