nullmailer, cron email & email provider requiring appropriate "From" field

[Johannes Graumann <johannes_graumann@web.de>]

Hello,

I have setup nullmailer on a debian stable system of mine to forward email 
to the smtp server of my mykolab.com account. That account requires that 
"From" in the header matches the account email.
Cron on my system insists to send email (as e.g. produced by a logcheck cron 
job) using "From" as derived from the user the executed script runs under 
("logcheck", in this case) and the provider accordingly refuses the email.

Googling leeds to the conclusion, that while cron on debian (stable) is 
accepting "MAILTO" in crontab, it doesn't accept "MAILFROM", which other 
distributions (Centos?) seem to have ...

Can anyone propose an elegant way to solve this issue?

Thank you for your consideration,

Sincerely, Joh