Again, most businesses and probably educational institutions as well would probably be comfortable with this kind of a block. Businesses might draw the line here, but academic institutions probably would be OK with this. Those containing religious proselytizing messages. Note that these header lines are not the headers fed through the SMTP transaction handshake. Note that this kind of a block is very dangerous because it blocks mail from legitimate mailing lists and alias lists.
Type make install to install procmail into the system.
The patches that the ports installer applies are required. One big problem with procmail is that it allocates memory in little-bitty 32K chunks and reallocates after each chunk. The patched version changes this to 4MB chunks, which work far more efficiently and greatly reduce the amount of real memory committed under FreeBSD's merged-VM cache design. Procmail must be installed as the local delivery agent. This is done by modifying the sendmail.mc file and regenerating the sendmail.cf file, as I have explained in previous articles.