Description of problem:
to quote bug 1325088#c8

"Yes, unfortunately cron has a bug that makes it to treat VAR=  lines as erroneous although according to the manual page it should be accepted."

I came across this while trying various MAILTO= values ...

Version-Release number of selected component (if applicable):
cronie-1.4.11-17.el7

How reproducible:
always

Steps to Reproduce:
1. modify /etc/crontab to include 'MAILTO=' line and a job that produces some output
2. wait
3. check root's mail

Actual results:
root gets mail with output of the job

Expected results:
root shouldn't get the output of the job

Additional info:
`man 5 crontab`

An active line in a crontab is either an environment setting or a cron command.  An environment setting is of the form:

          name = value

       where  the  white  spaces around the equal-sign (=) are optional, and any subsequent non-leading white spaces in value is a part of the value assigned to name.  The value string may be placed in quotes (single or double, but matching) to preserve leading or trailing white spaces.

...

If MAILTO is defined but empty (MAILTO=""), no mail is sent.


^ according to the way environment settings should be parsed, the following three should be equal:

MAILTO=""
MAILTO=''
MAILTO=