Can I Get Users to Verify Before Sending Credit Card Numbers?

Yes. Both SendGuard Pro and SendGuard Premium allow you to scan emails for sensitive information such as MasterCard, Visa, US Social Security Numbers (SSN), and many others. You can configure this using the Data Loss Prevention (DLP) feature. 
Here’s how to set it up:

Step-by-Step: Creating a DLP Rule for MasterCard Detection 

  1. Log in to the SendGuard Management Console 
     Go to: https://standsssaas.azurewebsites.net/ 
  2. Select Your Subscription 
     Once logged in, choose your subscription from the list and click Manage to view its details. 
  3. Navigate to M365 Settings 
     Click on the M365 Settings tab. 
  4. Scroll to the Data Loss Prevention Section 
  5. Create a New Rule 
     Click the Create New Rule button. A setup prompt will appear with four sections to complete: 
a.    Rule Settings 
I. Rule Name: Enter a name like "Detect MasterCard Numbers" 
II. Rule Type: Select DLP Rule 
III. Rule Status: This is enabled by default 
IV. Click Next

b.    Rule Conditions 
I. Rule Condition: From the dropdown, select Credit Card – MasterCard 
II. Regular Expression: Leave as is 
III. Click Next

c.    Rule Actions 
I. Choose one of the following actions:
 Block Sending – Prevents the email from being sent 
 Type Send – User must type “send” to confirm 
 Checkbox – User must check a box to confirm 
II. Click Next

d.    Review and Finish 
I. Review your settings 
II. Click Finish

Once this rule is set up, try typing a MasterCard number into an email and click Send. SendGuard will detect the card number and prompt the user based on your selected action.