feat: support DKIM (#129)

vitepress-docs/docs/en/cli.md

@@ -1,5 +1,7 @@
 # cloudflare temp email
 
+This is a temporary email service that uses Cloudflare Workers to create a temporary email address and view the received email in web browser.
+
 ## Features
 
 - [x] Cloudflare D1 as a database
@@ -14,6 +16,7 @@
 - [x] Add attachment viewing function
 - [x] use rust wasm to parse email
 - [x] support send email
+- [x] support DKIM
 
 ## Deploy
 
@@ -101,3 +104,27 @@ Create a new `_mailchannels` record, the type is `TXT`, the content is `v=mc1 cf
 
 - The worker domain name here is the domain name of the back-end api. For example, if I deploy it at `https://temp-email-api.awsl.uk/`, fill in `v=mc1 cfid=awsl.uk`
 - If your domain name is `https://temp-email-api.xxx.workers.dev`, fill in `v=mc1 cfid=xxx.workers.dev`
+
+
+## Configure DKIM
+
+Ref: [Adding-a-DKIM-Signature](https://support.mailchannels.com/hc/en-us/articles/7122849237389-Adding-a-DKIM-Signature)
+
+Creating a DKIM private and public key:
+Private key as PEM file and base64 encoded txt file:
+
+```bash
+openssl genrsa 2048 | tee priv_key.pem | openssl rsa -outform der | openssl base64 -A > priv_key.txt
+```
+
+Public key as DNS record:
+
+```bash
+echo -n "v=DKIM1;p=" > pub_key_record.txt && \
+openssl rsa -in priv_key.pem -pubout -outform der | openssl base64 -A >> pub_key_record.txt
+```
+
+Add `TXT` record in `Cloudflare` all your mail domain `DNS`
+
+- `_dmarc`: `v=DMARC1; p=none; adkim=r; aspf=r;`
+- `mailchannels._domainkey`: `v=DKIM1; p=<content of the file pub_key_record.txt>`