Creating a temporary SMTP server to 'catch' domain validation emails

One problem that has come up a time or two is dealing with email-based domain validation (specifically in this case for the issuance of TLS certificates) on domains that aren’t actually configured to receive email. Yes, in a perfect world, it would be easier to switch to DNS-based validation (since we have to have control of the DNS for the domain, we need it later), but let’s just assume that’s not an option. So, how do we ‘catch’ the activation email so we can prove we can receive email on that domain?


Parsing AWS instance data with jq

Semi-random amusing code snippet of the day:

aws ec2 describe-instances | jq << EOF
    .[][].Instances[]
    | select(.Tags[]?.Value == "production")
    | .PrivateIpAddress
EOF