I finally got this issue to work tonight and thought I'd post it for all others that are experiencing the same.
1- If you are using GMail, you have to setup an 'App Password' for your Canon to work.
2- Go to Google.com and click on your picture (upper right hand corner) and select 'Manage Your Google Account'.
3- Click on 'Security on the left hand side'.
4- Scroll down to section that says 'Signing in to Google'.
5- Make sure '2-Step Verification' is setup. If it is not, add 2-step verification now.
6- Click on 'App Passwords' to setup a password for your Canon. You may have to sign into your Google account again.
7- Under the 'Select App' down arrow, select 'Other (custom)'
8- Enter a name for your Cannon. I put my model number in the field: MF644Cdw
9- Select the 'Generate' button. This will generate a password. Copy/Paste this password or write it down.
10- Find your Cannon's IP Address. I selected 'Status Monitor' on my Cannon; then selected 'Network Information'; then selected 'IPv4'; take down the numbers listed under 'IP Address'.
11- Open up Chrome and enter the IP Address from step 10.
12- Select 'System Manager Mode' option and select 'Log In'. If you have setup a 'System Manager ID' and 'System Manager PIN', enter that information and then select 'Log In'.
13- Select 'Settings/Registration' button on the right hand side.
14- Select 'TX Settings' on the left hand side.
15- Select 'E-mail/I-Fax Settings'.
16- Select 'Edit' button on the upper right hand side.
17- SMTP server = smtp.gmail.com
18- Email Address = [enter your email address]
19- Check mark 'Use SMTP Authentication (SMTP AUTH)'
20- User Name = [enter your email address]
21- Check mark 'Set/Change Password'
22- Password = [enter the password generated from step 9 above]
23- Check mark 'Use TLS for SMTP'
24- Check mark 'Verify Certificate'
25- Check mark 'Add CN to Verification Items'
26- Check mark 'Use TLS for POP'
27- Check mark 'Verify Certificate'
28- Check mark 'Add CN to Verification Items'
29- Scroll up to the top of the page and select the 'OK' button to save these settings.
30- Select 'Network Settings' on left hand side.
31- Select 'Port Number Settings'
32- Select 'Edit' button in upper right hand side.
33- Change 'SMTP' field to = 465
34- Scroll up to the top of the page and select the 'OK' button to save these settings.
35- Select 'To Portal' link in the upper right hand corner.
36- Select 'Address Book' button on right hand side.
37- Click on '01' link and select 'Edit' button. Add your email as the first email address.
38- SCroll up to the top of the page and select the 'OK' button to save these settings.
39- Go to your Cannon and test the Scan to Email function.
40- Check email to see if you received the email. If you didn't get email, check 'Status Monitor/Cancel' button under the 'TX Job Log' section for Error Code specifics.
