Spam can cause problems with exim when it is both incoming and outgoing. Recently, we started getting excessive resource usage notices for two different customers. At first, it looked like their mail accounts were being used to spam the server.

After further analysis, we realized it was actually that the domains were being bombarded with spam to their accounts. Exim was raising the server load dramatically, because neither account had the default address set to :fail: no such address here. Continue Reading »