diff --git a/src/mailsrv/docs/Resources.md b/src/mailsrv/docs/Resources.md
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+# Resources
+
+## SPF, DKIM, and DMARC mail protection
+
+- https://www.digitalocean.com/community/tutorials/how-to-use-an-spf-record-to-prevent-spoofing-improve-e-mail-reliability
+- https://www.linuxbabe.com/mail-server/setting-up-dkim-and-spf
+  - says to use `@` for subdomain, but Dyn only accepts `*` as wildcard
+- https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-dkim-with-postfix-on-debian-wheezy
+- https://www.linuxbabe.com/mail-server/create-dmarc-record