Why is my SMTP slow to respond when I first connect?

[admin]

The most common cause for this is the Transaction Delays SPAM Filter which causes SMTP transaction delays in order to evade impatient SPAM clients which will often timeout after a short delay. This can be quite a harsh security measure and it is often necessary to disable or shortened this delay for busy servers. Another cause for an initial SMTP delay is that you are attempting to use the SPAM RBL service named 'ORDB'. In January 2007, this RBL went offline and any installation which still attempts to access this database can cause new SMTP connections to delay for up to 30 seconds before responding. In version 2.58 we automatically disabled this RBL but this can also be manually achieved by simply accessing the SPAM filtering settings and removing the ORDB entry from the list of RBLs.