diff --git a/main.go b/main.go
index efea55e..84cd1f2 100644
--- a/main.go
+++ b/main.go
@@ -108,6 +108,11 @@ func main() {
 			Usage:  "attachment filename(s)",
 			EnvVar: "PLUGIN_ATTACHMENTS",
 		},
+		cli.StringFlag{
+			Name:   "evaluate",
+			Usage:  "evaluation expression",
+			EnvVar: "PLUGIN_EVALUATE",
+		},
 		cli.StringFlag{
 			Name:   "clienthostname",
 			Value:  DefaultClientHostname,
@@ -347,6 +352,7 @@ func run(c *cli.Context) error {
 	}
 
 	plugin := Plugin{
+		Context: c,
 		Repo: Repo{
 			FullName: c.String("repo.fullName"),
 			Owner:    c.String("repo.owner"),
@@ -421,6 +427,7 @@ func run(c *cli.Context) error {
 			Attachment:     c.String("attachment"),
 			Attachments:    c.StringSlice("attachments"),
 			ClientHostname: c.String("clienthostname"),
+			Evaluation:     c.String("evaluate"),
 		},
 	}
 
diff --git a/plugin.go b/plugin.go
index 03c0079..51ac460 100644
--- a/plugin.go
+++ b/plugin.go
@@ -3,12 +3,15 @@ package main
 import (
 	"bufio"
 	"crypto/tls"
+	"fmt"
 	"os"
 
 	log "github.com/Sirupsen/logrus"
+	"github.com/antonmedv/expr"
 	"github.com/aymerick/douceur/inliner"
 	"github.com/drone/drone-go/template"
 	"github.com/jaytaylor/html2text"
+	"github.com/urfave/cli"
 	gomail "gopkg.in/mail.v2"
 )
 
@@ -97,9 +100,11 @@ type (
 		Attachment     string
 		Attachments    []string
 		ClientHostname string
+		Evaluation     string
 	}
 
 	Plugin struct {
+		Context     *cli.Context
 		Repo        Repo
 		Remote      Remote
 		Commit      Commit
@@ -116,6 +121,28 @@ type (
 
 // Exec will send emails over SMTP
 func (p Plugin) Exec() error {
+	if p.Config.Evaluation != "" {
+		env := p.Environ()
+
+		fmt.Printf("%+v\n", expr.Env(env))
+
+		out, err := expr.Compile(p.Config.Evaluation, expr.Env(env), expr.AsBool())
+
+		if err != nil {
+			return err
+		}
+
+		result, err := expr.Run(out, env)
+
+		if err != nil {
+			return err
+		}
+
+		if result.(bool) == false {
+			return nil
+		}
+	}
+
 	var dialer *gomail.Dialer
 
 	if !p.Config.RecipientsOnly {
@@ -244,6 +271,48 @@ func (p Plugin) Exec() error {
 	return nil
 }
 
+func (p Plugin) Environ() map[string]string {
+	return map[string]string{
+		"CI_REPO_OWNER":             p.Context.String("repo.owner"),
+		"CI_REPO_NAME":              p.Context.String("repo.name"),
+		"CI_REPO_SCM":               p.Context.String("repo.scm"),
+		"CI_REPO_LINK":              p.Context.String("repo.link"),
+		"DRONE_REPO_AVATAR":         p.Context.String("repo.avatar"),
+		"CI_REPO_DEFAULT_BRANCH":    p.Context.String("repo.branch"),
+		"CI_REPO_PRIVATE":           p.Context.String("repo.private"),
+		"DRONE_REPO_TRUSTED":        p.Context.String("repo.trusted"),
+		"CI_REPO_CLONE_URL":         p.Context.String("remote.url"),
+		"CI_COMMIT_SHA":             p.Context.String("commit.sha"),
+		"CI_COMMIT_REF":             p.Context.String("commit.ref"),
+		"CI_COMMIT_BRANCH":          p.Context.String("commit.branch"),
+		"CI_COMMIT_LINK":            p.Context.String("commit.link"),
+		"CI_COMMIT_MESSAGE":         p.Context.String("commit.message"),
+		"CI_COMMIT_AUTHOR":          p.Context.String("commit.author.name"),
+		"CI_COMMIT_AUTHOR_EMAIL":    p.Context.String("commit.author.email"),
+		"CI_COMMIT_AUTHOR_AVATAR":   p.Context.String("commit.author.avatar"),
+		"CI_BUILD_NUMBER":           p.Context.String("build.number"),
+		"CI_BUILD_EVENT":            p.Context.String("build.event"),
+		"CI_PIPELINE_STATUS":        p.Context.String("build.status"),
+		"CI_PIPELINE_LINK":          p.Context.String("build.link"),
+		"CI_PIPELINE_CREATED":       p.Context.String("build.created"),
+		"CI_PIPELINE_STARTED":       p.Context.String("build.started"),
+		"CI_PIPELINE_FINISHED":      p.Context.String("build.finished"),
+		"CI_PREV_PIPELINE_STATUS":   p.Context.String("prev.build.status"),
+		"CI_PREV_PIPELINE_NUMBER":   p.Context.String("prev.build.number"),
+		"CI_PREV_COMMIT_SHA":        p.Context.String("prev.commit.sha"),
+		"CI_STEP_NUMBER":            p.Context.String("job.number"),
+		"CI_STEP_STATUS":            p.Context.String("job.status"),
+		"DRONE_JOB_EXIT_CODE":       p.Context.String("job.exitCode"),
+		"CI_STEP_STARTED":           p.Context.String("job.started"),
+		"CI_STEP_FINISHED":          p.Context.String("job.finished"),
+		"DRONE_YAML_SIGNED":         p.Context.String("yaml.signed"),
+		"DRONE_YAML_VERIFIED":       p.Context.String("yaml.verified"),
+		"CI_COMMIT_TAG":             p.Context.String("tag"),
+		"CI_COMMIT_PULL_REQUEST":    p.Context.String("pullRequest"),
+		"CI_PIPELINE_DEPLOY_TARGET": p.Context.String("deployTo"),
+	}
+}
+
 func attach(message *gomail.Message, attachment string) {
 	if _, err := os.Stat(attachment); err == nil {
 		message.Attach(attachment)