It would be helpful at times to have a "not" operator to go with the mailgun routes. I run across this at times when trying to keep unwanted email traffic off my server. Say I am matching recipients in my routes. For a simple ruleset I can just match the recipients I want, and never see those emails that don't match. For more complicated rulesets I may want to throw out some or all of the addresses I don't want, and then further process the remaining addresses to route them. The ones I don't want are usually most easily defined as not matching the regular expressions describing those I do want. Even if a regexp to match a certain pattern is fairly simple, writing and maintaining a regular expression to not match that same pattern can be very involved. Having a not(match_recipient('regex')) would be much simpler. Currently I just receive the extraneous emails on my server via mailgun post, and ignore those that are unwanted. But clearly that results in additional traffic on my server and on the mailgun servers as compared to mailgun rejecting them earlier in the process.