Description of problem:

Run emacs
Use "M-X rmail" to run rmail.
It says that you have no mail even if there is mail in your /var/spool/mail/ file.
If you force the spool file, for example with the line below in $HOME/.emacs
(setq rmail-primary-inbox-list "/var/spool/mail/william")
then rmail gives the error "Invalid mbox file¨.
I can read my mail with other applications, so the problem is emacs-rmail and not the file format.
I get mail with a cron job that runs fetchmail, and then I think that fetchmail forwards the mail to sendmail which writes it into the mail spool file.

Version-Release number of selected component (if applicable):

sony ~$ rpm -qa | grep '^emacs'
emacs-common-24.0.97-1.fc17.x86_64
emacs-filesystem-24.0.97-1.fc17.x86_64
emacs-24.0.97-1.fc17.x86_64
sony ~$ rpm -qa | grep '^fetchmail'
fetchmail-6.3.21-2.fc17.x86_64
sony ~$ rpm -qa | grep '^sendmail'
sendmail-cf-8.14.5-12.fc17.noarch
sendmail-8.14.5-12.fc17.x86_64
sony ~$ uname -a
Linux sony 3.4.3-1.fc17.x86_64 #1 SMP Mon Jun 18 19:53:17 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

How reproducible:

Happens every time.

Steps to Reproduce:
1. Send your self mail.
2. Wait for the mail to arrive in your var spool mail file.
3. Run emacs and start rmail with M-X rmail.
  
Actual results:

It says that your mail file has no messages.

Expected results:

It should show the messages.

Additional info:

I looked on google and didn't see anything specific to this problem, but I did see a related issue where emacs can corrupt files if you configure it to ensure that files end with a newline.  I have not set that option.