@@ -3,6 +3,7 @@
 go 1.16
 
 require (
+	blitiri.com.ar/go/spf v1.2.0
 	github.com/go-shiori/go-readability v0.0.0-20210627123243-82cc33435520
 	github.com/gomodule/redigo v1.8.5
 	github.com/joegrasse/mail v1.0.0

@@ -1,3 +1,5 @@
+blitiri.com.ar/go/spf v1.2.0 h1:aPpeEVKz5Ue4xb4SEt4AzScCSyES7/pol6znzZGle3A=
+blitiri.com.ar/go/spf v1.2.0/go.mod h1:HLmgHxdrsqbBgi5omEopdAKm18PypvUKJGkF/j7BO0w=
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
@@ -174,8 +176,9 @@ gopkg.in/resty.v1 v1.12.0/go.mod h1:mDo4pnntr5jdWRML875a/NmxYqAlA73dVijT2AXvQQo=
 gopkg.in/yaml.v2 v2.0.0-20170812160011-eb3733d160e7/go.mod h1:JAlM8MvJe8wmxCU4Bli9HhUf9+ttbYbLASfIpnQbh74=
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v2 v2.2.4 h1:/eiJrUcujPVeJ3xlSWaiNi3uSVmDGBK1pDHUHAnao1I=
 gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.3.0 h1:clyUAQHOM3G0M3f5vQj7LuJrETvjVot3Z5el9nffUtU=
+gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 mvdan.cc/xurls/v2 v2.3.0 h1:59Olnbt67UKpxF1EwVBopJvkSUBmgtb468E4GVWIZ1I=
 mvdan.cc/xurls/v2 v2.3.0/go.mod h1:AjuTy7gEiUArFMjgBBDU4SMxlfUYsRokpJQgNWOt3e4=

@@ -0,0 +1,50 @@
+package mail
+
+import (
+	"fmt"
+	"net"
+	"net/mail"
+	"strings"
+
+	"blitiri.com.ar/go/spf"
+	"golang.org/x/net/idna"
+)
+
+func VerifySPF(email string) (bool, error) {
+	e, err := mail.ParseAddress(email)
+	if err != nil {
+		return false, fmt.Errorf("parse address: %w", err)
+	}
+	domain := strings.Split(e.Address, "@")[1]
+
+	domain, err = idna.ToASCII(domain)
+	if err != nil {
+		return false, fmt.Errorf("to ascii: %w\n", err)
+	}
+
+	mxs, err := net.LookupMX(domain)
+	if err != nil {
+		return false, fmt.Errorf("mx lookup: %w\n", err)
+	}
+
+	passes := []spf.Result{}
+	for _, mx := range mxs {
+		ips, err := net.LookupIP(mx.Host)
+		if err != nil {
+			return false, fmt.Errorf("ip lookup: %w\n", err)
+		}
+
+		for _, ip := range ips {
+			result, _ := spf.CheckHostWithSender(ip, domain, e.Address)
+			if result == spf.Pass {
+				passes = append(passes, result)
+			}
+		}
+	}
+
+	if len(passes) > 0 {
+		return true, nil
+	} else {
+		return false, nil
+	}
+}

@@ -55,6 +55,5 @@ err = email.Send(SMTP_HOST + ":" + SMTP_PORT)
 	if err != nil {
 		return err
 	}
-
 	return nil
 }

@@ -21,37 +21,46 @@ log.Printf("using body as is: %v\n", err)
 			body = m.Body
 		}
 
-		urls := mail.ExtractURLs(body)
-		if len(urls) == 0 {
-			log.Printf("no urls found")
+		spf, err := mail.VerifySPF(m.From)
+		if err != nil {
+			log.Printf("verify spf: %v", err)
 		}
-		for _, u := range distinct(urls) {
-			log.Printf("url: %s\n", u)
-			parsedURL, err := url.Parse(u)
-			if err != nil {
-				log.Printf("url parse: %v\n", err)
-			}
 
-			f, err := reader.Fetch(parsedURL.String())
-			if err != nil {
-				log.Printf("reader fetch: %v\n", err)
+		if spf {
+			urls := mail.ExtractURLs(body)
+			if len(urls) == 0 {
+				log.Printf("no urls found")
 			}
+			for _, u := range distinct(urls) {
+				log.Printf("url: %s\n", u)
+				parsedURL, err := url.Parse(u)
+				if err != nil {
+					log.Printf("url parse: %v\n", err)
+				}
 
-			article, err := reader.Readable(f, parsedURL)
-			if err == nil {
-				err = mail.SendArticle(&article, m.From, true)
+				f, err := reader.Fetch(parsedURL.String())
 				if err != nil {
-					log.Printf("error sending mail to: %s: %v\n", m.From, err)
+					log.Printf("reader fetch: %v\n", err)
+				}
+
+				article, err := reader.Readable(f, parsedURL)
+				if err == nil {
+					err = mail.SendArticle(&article, m.From, true)
+					if err != nil {
+						log.Printf("error sending mail to: %s: %v\n", m.From, err)
+					} else {
+						log.Printf("sent mail to %s: %s\n", m.From, article.Title)
+					}
 				} else {
-					log.Printf("sent mail to %s: %s\n", m.From, article.Title)
-				}
-			} else {
-				log.Printf("not readable: %s\n", err)
-				err := mail.SendArticle(&article, m.From, false)
-				if err != nil {
-					log.Printf("error sending mail to: %s: %v\n", m.From, err)
+					log.Printf("not readable: %s\n", err)
+					err := mail.SendArticle(&article, m.From, false)
+					if err != nil {
+						log.Printf("error sending mail to: %s: %v\n", m.From, err)
+					}
 				}
 			}
+		} else {
+			log.Printf("bad spf: %s", m.From)
 		}
 		w.WriteHeader(204)
 	})