If emails send via Design Manager are reported as never received, its recommend to first check any spam or junkmail folders.
This article highlights how to look in the junk folder and mark a message as safe for a few popular email providers.
Gmail Users:
- On your computer, open Gmail.
- On the left, click More.
- Click Spam.
- Open the email.
- At the top, click Not spam.
Tip: To stop a message from being sent to Spam in the future, you can:
Outlook.com and Hotmail Users
To mark an email message as Not junk in Outlook.com
Open your Junk Email folder and select the messages you want to keep.
From the top toolbar, select Not junk > Not junk (or Not spam > Not spam).
You can also open the message and select the It's not junk link at the top.
If you've blocked someone by mistake, open your Blocked senders list and select the 
next to their name.
Add the sender to your Safe senders list.
Click Settings > View all outlook settings
Click Mail > Junk Email > +Add the email to safe senders
Microsoft Outlook
1. Click on the Junk E-mail folder.
2. Select the email to mark as safe
3. Go to the Home tab, click Junk and select Not Junk from the dropdown menu
Alternatively, after selecting, right-click on the emails, go to junk and then click “Not Junk”
After clicking Not Junk, a Mark as Not Junk dialog box will pop up, please check the Always trust e-mail from “[email protected]" box and then click OK.