Support the deliveredto operator natively

README.md

@@ -307,6 +307,10 @@ the following common operators:
 * `cc`: the mail has the given address as CC destination
 * `bcc`: the mail has the given address as BCC destination
 * `replyto`: the mail has the given address as Reply-To destination
+* `deliveredto`: the mail was delivered to the given address, according to its
+  Delivered-To header. Useful to match `+` aliases (e.g. `me+tag@gmail.com`)
+  or mail coming from forwarding services, regardless of the recipients in
+  `to`. Note that it doesn't match Google Workspace domain aliases.
 
 One more special function is given if you need to use less common operators<sup
 id="a1">[1](#f1)</sup>, or want to compose your query manually:
@@ -645,6 +649,7 @@ as possible. This is the list of fields:
 * `cc: [<list>]`: a list of emails in cc.
 * `bcc: [<list>]`: a list of emails in bcc.
 * `replyto: <string>`: the email listed in the Reply-To field.
+* `deliveredto: [<list>]`: a list of emails in the Delivered-To headers.
 * `lists: [<list>]`: a list of mailing lists.
 * `subject: <string>`: the subject of the email.
 * `body: <string>`: the body of the email.

internal/engine/cfgtest/builder.go

@@ -56,7 +56,8 @@ func (r *evalBuilder) VisitLeaf(n *parser.Leaf) {
 	var rules []RuleEvaluator
 
 	switch n.Function {
-	case parser.FunctionFrom, parser.FunctionCc, parser.FunctionBcc, parser.FunctionList, parser.FunctionReplyTo:
+	case parser.FunctionFrom, parser.FunctionCc, parser.FunctionBcc, parser.FunctionList,
+		parser.FunctionReplyTo, parser.FunctionDeliveredTo:
 		rules = expandAll(n.Args, func(a string) RuleEvaluator {
 			return emailField(toMatchField(n.Function), a)
 		})
@@ -188,6 +189,8 @@ func toMatchField(f parser.FunctionType) matchField {
 		return matchFieldBcc
 	case parser.FunctionReplyTo:
 		return matchFieldReplyTo
+	case parser.FunctionDeliveredTo:
+		return matchFieldDeliveredTo
 	case parser.FunctionList:
 		return matchFieldLists
 	case parser.FunctionSubject:

internal/engine/cfgtest/eval.go

@@ -24,6 +24,7 @@ const (
 	matchFieldCc
 	matchFieldBcc
 	matchFieldReplyTo
+	matchFieldDeliveredTo
 	matchFieldLists
 	matchFieldSubject
 	matchFieldBody
@@ -91,6 +92,8 @@ func (n funcNode) Match(msg cfg.Message) bool {
 		fields = msg.Bcc
 	case matchFieldReplyTo:
 		fields = msg.ReplyTo
+	case matchFieldDeliveredTo:
+		fields = msg.DeliveredTo
 	case matchFieldLists:
 		fields = msg.Lists
 	case matchFieldSubject:

internal/engine/cfgtest/eval_test.go

@@ -20,6 +20,7 @@ func TestEmailFieldMatching(t *testing.T) {
 		{parser.FunctionCc, func(s string) cfg.Message { return cfg.Message{Cc: []string{s}} }},
 		{parser.FunctionBcc, func(s string) cfg.Message { return cfg.Message{Bcc: []string{s}} }},
 		{parser.FunctionReplyTo, func(s string) cfg.Message { return cfg.Message{ReplyTo: []string{s}} }},
+		{parser.FunctionDeliveredTo, func(s string) cfg.Message { return cfg.Message{DeliveredTo: []string{s}} }},
 		{parser.FunctionList, func(s string) cfg.Message { return cfg.Message{Lists: []string{s}} }},
 		{parser.FunctionHas, func(s string) cfg.Message { return cfg.Message{From: s} }},
 	}

internal/engine/cfgtest/testdata/pass.jsonnet

@@ -63,6 +63,17 @@ local filters = {
         delete: true,
       }
     },
+    {
+      filter: {
+        or: [
+          {deliveredto: 'pippo+shopping@gmail.com'},
+          {deliveredto: 'pippo+deals@gmail.com'},
+        ]
+      },
+      actions: {
+        labels: ['shopping'],
+      }
+    },
   ],
   tests: [
     {
@@ -114,5 +125,18 @@ local filters = {
         labels: ['maillist', 'onemorelabel'],
       },
     },
+    {
+      name: 'forwarded aliases',
+      messages: [
+        {
+          to: ['store@simplelogin.com'],
+          deliveredto: ['pippo+shopping@gmail.com'],
+        },
+        {deliveredto: ['pippo+deals@gmail.com']},
+      ],
+      actions: {
+        labels: ['shopping'],
+      },
+    },
   ],
 }

internal/engine/config/v1alpha3/config.go

@@ -30,15 +30,16 @@ type FilterNode struct {
 	Or  []FilterNode `json:"or,omitempty"`
 	Not *FilterNode  `json:"not,omitempty"`
 
-	From    string `json:"from,omitempty"`
-	To      string `json:"to,omitempty"`
-	Cc      string `json:"cc,omitempty"`
-	Bcc     string `json:"bcc,omitempty"`
-	ReplyTo string `json:"replyto,omitempty"`
-	Subject string `json:"subject,omitempty"`
-	List    string `json:"list,omitempty"`
-	Has     string `json:"has,omitempty"`
-	Query   string `json:"query,omitempty"`
+	From        string `json:"from,omitempty"`
+	To          string `json:"to,omitempty"`
+	Cc          string `json:"cc,omitempty"`
+	Bcc         string `json:"bcc,omitempty"`
+	ReplyTo     string `json:"replyto,omitempty"`
+	DeliveredTo string `json:"deliveredto,omitempty"`
+	Subject     string `json:"subject,omitempty"`
+	List        string `json:"list,omitempty"`
+	Has         string `json:"has,omitempty"`
+	Query       string `json:"query,omitempty"`
 
 	// IsEscaped specifies that the given parameters don't need any
 	// further escaping.
@@ -147,14 +148,15 @@ type Test struct {
 
 // Message represents the contents and metadata of an email.
 type Message struct {
-	From    string   `json:"from,omitempty"`
-	To      []string `json:"to,omitempty"`
-	Cc      []string `json:"cc,omitempty"`
-	Bcc     []string `json:"bcc,omitempty"`
-	ReplyTo []string `json:"replyto,omitempty"`
-	Lists   []string `json:"lists,omitempty"`
-	Subject string   `json:"subject,omitempty"`
-	Body    string   `json:"body,omitempty"`
+	From        string   `json:"from,omitempty"`
+	To          []string `json:"to,omitempty"`
+	Cc          []string `json:"cc,omitempty"`
+	Bcc         []string `json:"bcc,omitempty"`
+	ReplyTo     []string `json:"replyto,omitempty"`
+	DeliveredTo []string `json:"deliveredto,omitempty"`
+	Lists       []string `json:"lists,omitempty"`
+	Subject     string   `json:"subject,omitempty"`
+	Body        string   `json:"body,omitempty"`
 }
 
 func jsonTagName(t reflect.StructTag) string {

internal/engine/filter/convert.go

@@ -160,6 +160,10 @@ func generateLeaf(leaf *parser.Leaf) (Criteria, error) {
 		return Criteria{
 			Query: fmt.Sprintf("replyto:%s", query),
 		}, nil
+	case parser.FunctionDeliveredTo:
+		return Criteria{
+			Query: fmt.Sprintf("deliveredto:%s", query),
+		}, nil
 	case parser.FunctionList:
 		return Criteria{
 			Query: fmt.Sprintf("list:%s", query),

internal/engine/filter/convert_test.go

@@ -189,6 +189,44 @@ func TestQuoting(t *testing.T) {
 	assert.Equal(t, expected, got)
 }
 
+func TestDeliveredTo(t *testing.T) {
+	tests := []struct {
+		name     string
+		criteria parser.CriteriaAST
+		want     Criteria
+	}{
+		{
+			name: "grouped leaf",
+			criteria: &parser.Leaf{
+				Function: parser.FunctionDeliveredTo,
+				Grouping: parser.OperationOr,
+				Args:     []string{"me+a@gmail.com", "me+b@gmail.com"},
+			},
+			want: Criteria{Query: "deliveredto:{me+a@gmail.com me+b@gmail.com}"},
+		},
+		{
+			name: "nested leaf",
+			criteria: &parser.Node{
+				Operation: parser.OperationNot,
+				Children: []parser.CriteriaAST{
+					&parser.Leaf{
+						Function: parser.FunctionDeliveredTo,
+						Args:     []string{"me+a@gmail.com"},
+					},
+				},
+			},
+			want: Criteria{Query: "-deliveredto:me+a@gmail.com"},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := GenerateCriteria(tt.criteria)
+			assert.Nil(t, err)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}
+
 func TestSplitLeaf(t *testing.T) {
 	rule := parser.Rule{
 		Criteria: &parser.Leaf{

internal/engine/parser/ast.go

@@ -36,6 +36,7 @@ const (
 	FunctionCc
 	FunctionBcc
 	FunctionReplyTo
+	FunctionDeliveredTo
 	FunctionSubject
 	FunctionList
 	FunctionHas
@@ -59,6 +60,8 @@ func (f FunctionType) String() string {
 		return "bcc"
 	case FunctionReplyTo:
 		return "replyto"
+	case FunctionDeliveredTo:
+		return "deliveredto"
 	case FunctionSubject:
 		return "subject"
 	case FunctionList:

internal/engine/parser/parser.go

@@ -143,6 +143,9 @@ func parseFunction(f cfg.FilterNode) (FunctionType, string) {
 	if f.ReplyTo != "" {
 		return FunctionReplyTo, f.ReplyTo
 	}
+	if f.DeliveredTo != "" {
+		return FunctionDeliveredTo, f.DeliveredTo
+	}
 	if f.Subject != "" {
 		return FunctionSubject, f.Subject
 	}