problem is a own mailer inside of the class newsletter. i make's no sense for me, because, wb has a good working mail function
multiple lines in class.newsletter.ph
p on different places - search for
if ($this->textOnly)original
if ($this->textOnly) {
$result = $this->mail($this->fromEMail,$this->fromEMail,nl_subject_admin_send_link, sprintf(nl_mail_admin_send_link,$this->toEMail,$thisLink)); }
else {
$result = $wb->mail($this->fromEMail,$this->fromEMail,nl_subject_admin_send_link, sprintf(nl_mail_admin_send_link,$this->toEMail,$thisLink)); }
}
change to
$result = $wb->mail($this->fromEMail,$this->fromEMail,nl_subject_admin_send_link, sprintf(nl_mail_admin_send_link,$this->toEMail,$thisLink));
@ Rumen: the mail is on the way

one more...
if you get the message in frontend like
Invalid address: (setFrom) name(at)gmail(dot)com
you have the wrong droplet call
use
[[
NL-SignupForm?title=
Newsletter&from=
name@mail.com]]
red = Name of the Droplet
green = Name of the Group in MassMail
blue = mailadress of the admin for the newsletter, use here @ and point instead of [at] and (dot) like the module description