Recently had a question at work about the maximum number of recipients Sendmail would allow thru our in-house server. I wasn’t sure but knew I hadn’t personally configured a hard limit. Did some quick searching and stumbled upon confMAX_RCPT_PER_MESSAGE as the answer. I haven’t set it to anything in our config but didn’t know what the default limit was in Sendmail so I did some digging. Stumbled upon the following links of value (to me at least!)

Answer: infinite number. Sendmail doesn’t have a limit (now it does!)

Also stumbled upon’s version 5 Deployment Guide on running the m4 macro command to build a new file.