One of the things I ran into was the amount of spam I received. It gradually increased from a dozen per day to some 300 to 400 per day. At a certain point my server even crashed because it received some 6.000 email in a period of five minutes.

This meant I had to take some action. I use Plesk on my server and it has some standard options like white lists, black lists, spf filtering but also a DNSBL feature. This last feature give you the possibility of checking incoming emails against a spam database. I had not looked at the feature but after checking Google I found the site http://www.spamhaus.org. I offers a free to use service for low-volume non-commercial use. You just enter zen.spamhaus.org into you Plesk Mail configuration screen and suddenly the spam flood is stopped. My spam went down from a big flood to a small drizzle, some 2 to 5 per day.

Great service!