[SOLVED] Account emails with Mandrill don't work out-of-the-box like MailGun?

I typically use mailgun but switched to try mandrill (via mailchimp). My forgot password emails are getting denied:

[
    {
        "email": "a@a.com",
        "status": "rejected",
        "_id": "993d525555e9e74b8aa3fc5555555cadb768f5",
        "reject_reason": "unsigned"
    }
]

my email template:

import { Meteor } from 'meteor/meteor';
import { Accounts } from 'meteor/accounts-base';

const name = Meteor.settings.public.config.appName;
const email = `<${Meteor.settings.public.config.supportEmail}>`;
const from = `${Meteor.settings.public.config.supportName} ${Meteor.settings.public.config.supportEmail}`;
const emailTemplates = Accounts.emailTemplates;

emailTemplates.siteName = name;
emailTemplates.from = from;
emailTemplates.from_email = from;

emailTemplates.resetPassword = {
  subject() {
    return `[${name}] Reset Your Password`;
  },
  text(user, url) {
    const userEmail = user.emails[0].address;
    const urlWithoutHash = url.replace('#/', '');

    return `A password reset has been requested for the account related to this
    address (${userEmail}). To reset the password, visit the following link:
    \n\n${urlWithoutHash}\n\n If you did not request this reset, please ignore
    this email. If you feel something is wrong, please contact our support team:
    ${email}.`;
  },
};

UPDATE:

make sure you are using ALL of the correct credentials!!