It takes at least 15 minutes for email to reach me

Greylisting is an anti-spam feature of cPanel that allows us to delay inbound email for 15 minutes for email accounts that haven't emailed you before.  It can eliminate a massive amount of spam by itself but it also can cause annoyance due to delaying new emailers from reaching you for an initially short period of time.  To turn it on or off for a domain, you can go to your cPanel > Email> Configure Greylisting.

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