Do this after you switch your MX records, as changing MX records can sometimes undo this. If you make this change before changing the MX records, you will see the following error in the delivery logs, and mail will bounce back to the sender:
550-Please turn on SMTP Authentication in your mail client.
When switching your MX records to use SpamHero, cPanel users need to ensure that their mail server does not disable local mail delivery. Unfortunately, when cPanel sees that you've pointed your MX records elsewhere, it incorrectly assumes it should tell your mail server to no longer accept email for your domain.
To correct this, go the Email Routing page and select Local Mail Exchanger as shown here:
If you do not see these options on the page where you change your MX records, it indicates that you are using a different version of cPanel. If that is the case, look instead for a single checkbox that says " Always accept mail locally even if the primary mx does not point to this server" and make sure it is enabled.
While not required, we also recommend Creating a cPanel Filter to Stop Spammers From Bypassing SpamHero.