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README.md

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 # mailsecchk
-POSIX script for mail security checks of domain names
+
+A simple POSIX script for mail security checks against domain names.
+
+```
+Usage: ./mailsecchk.sh [OPTIONS]...
+check mail security of a given domain
+
+arguments:
+  -d domain to be checked
+  -h display this help and exit
+  -l log file to output to
+```
+
+## Current checks
+
+* SPF DNS record presence
+* SPF not using FAIL mode "-all"
+* DMARC DNS record presence
+* DMARC policy ("p")
+* DMARC subpolicy ("sp")
+* DMARC sample percentage ("pct")
+* DMARC aggregation and forensic reports send to third-parties ("rua" and "ruf")
+* DKIM dictionnary guess for selectors (list is in dkim_selectors.txt)
+
+Specific to Microsoft 365:
+
+* SPF set to include M365 SPF
+* DKIM presence (selectors are predictable)
+
+## Examples
+
+![example 1](img/altf8.png "Example 1")
+
+![example 2](img/lemonde.png "Example 2")