system/Validation/FormatRules.php
public function valid_emails(string $str = null): bool
	{
		foreach (explode(',', $str) as $email)
		{
			$email = trim($email);
			if ($email === '')
			{
				return false;
			}

			if ($this->valid_email($email) === false)
			{
				return false;
			}
		}

		return true;
	}
public function valid_emails(string $str = null): bool
	{
		foreach (explode(',', $str) as $email)
		{
			$email = trim($email);
			if ($email === '')
			{
				return false;
			}

			if ($this->valid_email($email) === false)
			{
				return false;
			}
		}

		return true;
	}
Validate a comma-separated list of email addresses.

Example:
valid_emails[one@example.com,two@example.com]

@param string

@return boolean