When doing nightly backups the sudo fails

[Basher52]

I get this: sudo: sorry, you must have a tty to run sudo

I found this by googling but can't fix it anyways.
I run the script by /etc/cron.daily/createbackup and when mailing the backup files I use sudo to get a better "sender" of the email than using root that seems to be marked as spam.

Alot of the posts say I should comment out this line in the sudoers file
Defaults requiretty

What does this line mean really?

[Void Main]

$ man sudoers

[Basher52]

Forgot about man again
found it and removed it
thx