*this configuration only apply if you are using the default Mail App included with Windows 10 and later

TL;DR (Too Long, Didn't Read)

Gather the info from our Control Panel by clicking the SMTP Auth Relay tab on the left menu.  You'll have to click the eye icon to view your passwords.  If you don't have a local password set up, you'll be asked to create one.  The Inbound (IMAP) and Outbound (SMTP) servers may have different logins and will have different passwords.   Go into your Mail app and add a new account email account using this info.

When you send email, click the From address to choose your new account for sending email.  It'll pass SPF, DKIM, DMARC checks.  Congratulations!

Long Version

Gather the info you need to configure your email client

To configure your email client to use the MailRoute SMTP Auth Relay service for outbound email relay, you will need to gather some info from the MailRoute Control Panel and then configure your email client. 

1. Login to admin.mailroute.net and click the My Settings link at the top of the page.
   
   
2. Click the SMTP Auth Relay tab in the Settings menu on the left side of the page. 
   
   
   
   
3. Gather your info!  You can click the copy icon  to copy the values of any field.
   
   For the Gmail webmail interface, you will only need the info in the Outbound (SMTP) Server configuration.
   
   
   Outbound (SMTP) Server Password:  Click the eye icon to display your password. Accept the Terms of Service:
   
            
   
   By the way, you can generate a new password for your Outbound (SMTP) Server at any time.

Configure your email client

1. Select Start , enter Mail, and choose the app from the results
   

2. If this is the first time you've opened the Mail app, you’ll see a Welcome page. Select Add account to get started.

   If you've used the Mail app before, at the bottom of the left navigation pane, select Settings icon, and then choose Manage Accounts
   
   

3. Select Advanced setup from the Choose an account window in Step 2 above. The Advanced setup option is the last option on the list, and you may have to scroll to see it.
   
   
4. Enter the following information in the Advanced setup window.
   
   Email address: This is the email address you're adding for SMTP Auth services

   
   User name:  <Your Inbound (IMAP) login>
   
   Password:  <Your Inbound (IMAP) password>
   
   Account Name: This is the name you'll see in the left pane of the Mail app and in the Manage Accounts pane. You can choose any name you want.
   
   Send your messages using this name: Enter the name you want recipients to see when they receive your message.
   
   Inbound Account type: IMAP4
   
   Incoming email server : <Your Inbound (IMAP) Server>
   
   IMAP Encryption: TLS

    

    

   Outgoing (SMTP) email server:   This is your server name, a colon, and the port.  
        So you'e going to enter:
        <Your Outbound (SMTP) Server>:<Your Outbound (SMTP) Port>
        That's going to be something like smtpauth.mailroute.net:587 
        Don't forget the colon between the two parts!
   
   Outgoing server requires authentication: selected
   
   User name: <Your Outbound (SMTP) Login>
   
   Password: <Your Outbound (SMTP) Password>
   
   SMTP Encryption: STARTTLS