E-Mail blacklist and whitelist NOT FINISHED for SMF 2.0.15 (partial file)

Profile-Modify.php

	// Check email providers
	if (!empty($modSettings['enable_restrict_EmailProvider']))
	{
		// Blacklisted email providers
		if (!empty($modSettings['restricted_provider']))
		{
			$restricted_provider = explode(",", $modSettings['restricted_provider']);
            
			// Iterate each blacklisted domain, and do housecleaning.
			foreach ($restricted_provider as $key => $value)
			{
				// If there is whitespace, remove it.
				$restricted_provider[$key] = trim($restricted_provider[$key]);
				
				// Remove empty elements in the array
				if (empty($restricted_provider[$key]))
					unset($restricted_provider[$key]);
			}
		}
		else
			$restricted_provider = array();
		
		// Check if the email is blacklisted
		foreach($restricted_provider as $provider)
		{
			if(strpos($email, $provider))
				fatal_error($txt['restricted'], false);
		}
		
		// Whitelisted email providers
		if (!empty($modSettings['accepted_provider']))
		{	
			$accepted_provider = explode(",", $modSettings['accepted_provider']);
		
			// Iterate each whitelisted domain, and do housecleaning.
			foreach ($accepted_provider as $key => $value)
			{
				// If there is whitespace, remove it.
				$accepted_provider[$key] = trim($accepted_provider[$key]);
				
				// Remove empty elements in the array
				if (empty($accepted_provider[$key]))
					unset($accepted_provider[$key]);
			}
		}
		else
			$accepted_provider = array(); 

		// If the foreach below is run, 
		// we check this variable to see if email was whitelisted
		$whitelist_pass = false;
		
		// Check if the email is whitelisted
		foreach($accepted_provider as $provider)
		{
			// Offset of 1 is used, so an empty email will not match (e.g. @gmail.com)
			$strpos_result = strpos($email, $provider, 1);
			
			// strpos have returned a value (we have a match)
			if($strpos_result !== FALSE)
			{
				// Verify that email provider is not a sub-domain
				if(empty($email[$strpos_result + strlen($provider)]))
				{
					$whitelist_pass = true; // Email is whitelisted
				}
			}
		}
		
		// Last check for whitelisted queries
		if(!empty($accepted_provider))
		{	
			if(!$whitelist_pass)
				fatal_error($txt['restricted'], false);
		}
	}

Subs-Members.php

	// Check email providers
	if (!empty($modSettings['enable_restrict_EmailProvider']))
	{
		// Blacklisted email providers
		if (!empty($modSettings['restricted_provider']))
		{
			$restricted_provider = explode(",", $modSettings['restricted_provider']);
            
			// Iterate each blacklisted domain, and do housecleaning.
			foreach ($restricted_provider as $key => $value)
			{
				// If there is whitespace, remove it.
				$restricted_provider[$key] = trim($restricted_provider[$key]);
				
				// Remove empty elements in the array
				if (empty($restricted_provider[$key]))
					unset($restricted_provider[$key]);
			}
		}
		else
			$restricted_provider = array();
		
		// Check if the email is blacklisted
		foreach($restricted_provider as $provider)
		{
			if(strpos($regOptions['email'], $provider))
				fatal_error($txt['restricted'], false);
		}
		
		// Whitelisted email providers
		if (!empty($modSettings['accepted_provider']))
		{	
			$accepted_provider = explode(",", $modSettings['accepted_provider']);
		
			// Iterate each whitelisted domain, and do housecleaning.
			foreach ($accepted_provider as $key => $value)
			{
				// If there is whitespace, remove it.
				$accepted_provider[$key] = trim($accepted_provider[$key]);
				
				// Remove empty elements in the array
				if (empty($accepted_provider[$key]))
					unset($accepted_provider[$key]);
			}
		}
		else
			$accepted_provider = array(); 

		// If the foreach below is run, 
		// we check this variable to see if email was whitelisted
		$whitelist_pass = false;
		
		// Check if the email is whitelisted
		foreach($accepted_provider as $provider)
		{
			// Offset of 1 is used, so an empty email will not match (e.g. @gmail.com)
			$strpos_result = strpos($regOptions['email'], $provider, 1);
			
			// strpos have returned a value (we have a match)
			if($strpos_result !== FALSE)
			{
				// Verify that email provider is not a sub-domain
				if(empty($regOptions['email'][$strpos_result + strlen($provider)]))
				{
					$whitelist_pass = true; // Email is whitelisted
				}
			}
		}
		
		// Last check for whitelisted queries
		if(!empty($accepted_provider))
		{	
			if(!$whitelist_pass)
				fatal_error($txt['restricted'], false);
		}
	}

If you are thinking about implementing this one, which have Blacklisting. There are several things which are not fixed.
I would say this one is a work in progress. (far from finished)
This newer one, and in my opinion the recommended one with only Whitelisting can be found here: https://gist.github.com/dalslandan200/192cddeeaf7cdb20661855be7fb00460
It should work as expected if correctly installed, without any issues.