[OT] PAM problems getting mails

Hello,

I know this isn't a getmail-specific problem, but asking on another list 
would imply too much context to be explained ...

Using arch linux, my user (peter) is in the wheel group.

On CLI I can get emails using:
sudo -E getmail

Using the same command in my personal crontab fails because of missing 
permissions (I'd have to add my password to the crontab ...).

So I tried to add the following line to /etc/crontab:
43 * * * *      root    su peter -c getmail

This fails, too:
Aug 24 12:43:01 tuchola CROND[7958]: (root) CMDOUT (Configuration error: 
configuration file /home/peter/.getmail/getmailrc incorrect (error 
opening message_log file ~/.getmail/log (Permission denied, opening file 
"~/.getmail/log")))

So, how can I start getmail using my user's environment (especially "~" 
as my home directory) with cron?

Kind regards

Peter