Q0412 - Exim/exim GitHub Wiki
Q0412
Why am I seeing the error bad mode (100664) for /home/test/.forward? I've looked through the documentation but can't see anything to suggest that Exim has to do anything other than read the .forward file.
For security, Exim checks for mode bits that shouldn't be set, by
default 022. You can change this by setting the modemask option of the
redirect router that is handling .forward files.