Add proper Mailx to verify smtp credentials

[steinbrueckri]

Mailx is not longer in the debian repos, we need to find a good solution to test something like this below.

export USER="x\A0001869"
export PASSWORD=""
export FROM_EMAIL_ADDRESS="x@x.de"
export TO_EMAIL_ADDRESS="steinbrueckri@x.com"

mailx -v -s "test" \
-S smtp-use-starttls \
-S smtp-auth=login \
-S smtp=smtp://smtprelay.x:587 \
-S from=$FROM_EMAIL_ADDRESS \
-S smtp-auth-user=$USER \
-S smtp-auth-password=$PASSWORD \
-S ssl-verify=ignore \
$TO_EMAIL_ADDRESS