SmarterMail's antispam options include greylisting, which is a very effective method of spam blocking that comes at a minimal price in terms of performance. When enabled, the system will keep track of the sending IP address, sending email address and recipient's email address for every message received. If an incoming message has a combination of a sending IP, sending address and recipient address that has not previously been seen, it will return a temporary failure to the sending server. This temporary failure essentially tells the sending server to “Try again later.” Valid servers will retry the email a short time later, at which point SmarterMail accepts the message. Spammers, on the other hand, typically create scripts that bombard your server with emails, and they rarely retry on temporary failures. When these messages are bounced back because of greylisting, they are typically not retried, therefore reducing the amount of spam that your customers receive.
In addition to the greylisting configuration on the Antispam | Options tab, administrators can use Greylist Filters to prevent greylisting based on the sender's country or IP address. To add an IP address or country code, click New. To edit an existing filter, simply click on it from the list. The following options will be available:
- Filter Type - Select the type of filter you would like to add: IP Address or Country Code.
- IP Address - If the filter type is set to IP Address, enter the IP address that should bypass greylisting / be greylisted.
- Country Code - If the filter type is set to Country Code, select a country code from the list. The greylisting exception / limitation will apply to all messages that are identified as coming from an IP address matching that country.
- Description - The friendly name or descriptor you want to give to the IPs. For example, Microsoft 365 or Yahoo!
Note: Some greylist filters are included by default and cannot be modified or removed. These default filters are indicated in the grid by having a checkmark in the Internal column.
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