Logwatch is not respecting MailFrom

I've gone through today to setup Logwatch on my server and have installed this all successfully.

I've followed this guide on Digital Ocean and set the MailFrom parameter to:

MailFrom = mailer@mydomain.com

I'm using ssmtp to send emails using my Postmark App account and it is coming through on my Postmark activity feed but it is showing the From field being set as root.

SMTP API Error for personaladdress@hotmail.com: Invalid 'From' address: 'root'.

Looking at the raw source of the email trying to be sent it shows this line:

From: root

This is the command I am using to generate the send:

sudo logwatch --detail Low --mailto personaladdress@hotmail.com --service http --range today

Where am I going wrong or what can I do to get it sending as mailer@mydomain.com as Postmark require the from address to be correctly sent otherwise it won't allow it through and returns an error

Further details

Logwatch version: Logwatch 7.4.0 (released 03/01/11)
System: Debian 8 (Jessie)
Using sSMTP on my server to send emails from Postmark
Debug log:

Config After Command Line Parsing:
supress_ignores -> 0
pathtozcat -> zcat
html_header -> /usr/share/logwatch/default.conf/html/header.html
logdir -> /var/log
hostlimit ->
encode -> none
subject ->
mailfrom -> root
format -> html
numeric -> 0
tmpdir -> /tmp
html_wrap -> 80
pathtobzcat -> bzcat
detail -> 0
range -> yesterday
hostformat -> none
debug -> 10
output -> mail
mailer -> /usr/sbin/sendmail -t
hostname -> game
html_footer -> /usr/share/logwatch/default.conf/html/footer.html
archives -> 1
pathtocat -> cat
mailto -> personal@hotmail.com
filename ->