Ever got your email sent to @yahoo returned — saying the Message blocked — see technical details?

It is because your domain might be missing a DKIM record hence Yahoo or other email servers think it’s a dangerous/unauthenticated email.

TLDR;
-Sent an email from an alias of a secondary domain 
-Message blocked/bounced back 
-Researched why it was blocked - my DKIM record was missing 
-Went to workspace and generated a DKIM record
-Went to domain cPanel and tried to add the TXT/DKIM record with 
 the Google-generated values
-String length was too long, can't add
-Learnt how to add a big string in a TXT record by splitting into two
-Returned to my Google workspace Admin Console to 'Start Authentication'
-Google says: It may take up to 48 hours for DNS changes to fully propagate.
-As I thought it Failed:Email authentication was not verified. 
 Please allow 48 hours for DNS to update and make sure that you entered 
 the correct TXT record into your domain provider's DNS settings page. 
-Wohoo it's done and working (within a few hours)! 

Recently, I ran into a frustrating issue that many small business owners and individuals might face when using their business email hosted on Google Workspace. I sent an email to a yahoo email id from an alias email of a secondary domain but the email bounced back. See the screenshot below.