Network Tools

Network and email-infrastructure tasks tend to involve arithmetic and lookups that are easy to get wrong by hand — calculating a subnet mask, expanding an IP range into the correct set of CIDR blocks, converting an IPv4 address between decimal and binary, or generating a properly-formatted IPv6 ULA prefix for a private network. The DNS Lookup, MX Record Checker, and SPF & DMARC Checker exist for the recurring job of diagnosing why email is landing in spam or why a domain's mail configuration doesn't match what a client swears they set up — checking these by hand means running multiple dig or nslookup commands and remembering what a valid SPF record actually looks like. The Email Header Analyzer decodes the routing and authentication information buried in raw headers, which is usually the fastest way to find out where a delivery actually failed. The TCP Capture Viewer handles a narrower but real need: reading a .pcap file's TCP conversations and handshakes without launching Wireshark for a single quick check. The DNS Propagation Checker exists because "did the DNS change go through yet" is a question every admin asks after every change, and checking it against multiple resolvers at once beats refreshing one lookup tool repeatedly.

As with the crypto tools, most of what you'd paste here — a mail header, an internal IP range — isn't something you want relayed through someone else's server, so none of it is.