We have an up to date, nicely configured Virtualmin Pro server. I have recently noticed quite a few junk messages getting through the filter.
I found that a certain class of junk was sneaking through the filter and not even getting any X-Spam headers added.
I tracked a message in /var/log/maillog and I found this:
Jul 17 18:21:12 www spamc: skipped message, greater than max message size (512000 bytes)
Sadly, it appears the spammers no longer care how large their messages are...
Apparently, and this seems to be key, the 'spamc' client that we are using gives a 'bypass' to messages larger than 512k. Further, the setting is apparently not in a config file, but is set on the 'spamc' command line as an argument '-s XXXXXXX'.
How should I go about implementing a 1M or greater setting? Something like '-s 2000000'.
Email Messages -> Spam and Virus Scanning -> Maximum message size to process
is already set at 'Unlimited', however Googling confirms what the error meaasge above implies: the default spamc limit is 512k.
Thanks in advance,