On new servers we use greylisting, grey listing will reduce the amount of spam but can have some drawbacks with wrongly configured servers.
Greylisting is the process where we temporary deny to receive email from unknown senders by sending the sender a message we can't receive email at the moment. As per mail RFC's the sender server needs to queue the email and try again in several minutes usually after 15 minutes. This is however a setting a mail administrator can set. Once the mail is send again within a certain timeframe we will accept mail from this person and ip in the future.
There are however several mails which will not be handled like this:
- mail from known large mail providers like gmail, yahoo, hotmail, outlook, and known providers used by our customers will be added when we see them.
- mails with a valid SPF record
In theory any email provider should by now have setup SPF records for their mail addresses, there is really no excuse not to do so ; anyone with a valid SPF will simply not being greylisted.
Note tht for the sending mail server we handle the mail as not being delivered, this means we do not receive any details about those mails, just like if the mail server which sends was not able to connect; this happens millions of times to any mailserver in the world so it is normal for a server to retry. Spammers however do not bother to have an official mailserver and just send out mails in masses ; these mails do not retry and therefor a lot of spam will never reach you anymore.
You can DISABLE greylisting for your domain in your cPanel ; note that disabling greylisting, it will be disabled for your whole account.
