diff --git a/internal/imapclient/service.go b/internal/imapclient/service.go
new file mode 100644
index 0000000..0c8edac
--- /dev/null
+++ b/internal/imapclient/service.go
@@ -0,0 +1,27 @@
+package imapclient
+
+import (
+	"context"
+
+	"email-mcp/internal/secretstore"
+)
+
+type Service struct {
+	backend Backend
+}
+
+func NewService(backend Backend) Service {
+	return Service{backend: backend}
+}
+
+func (s Service) ListMailboxes(ctx context.Context, cred secretstore.Credential) ([]Mailbox, error) {
+	return s.backend.ListMailboxes(ctx, cred)
+}
+
+func (s Service) ListMessages(ctx context.Context, cred secretstore.Credential, mailbox string, limit int) ([]MessageSummary, error) {
+	return s.backend.ListMessages(ctx, cred, mailbox, limit)
+}
+
+func (s Service) GetMessage(ctx context.Context, cred secretstore.Credential, mailbox string, id string) (Message, error) {
+	return s.backend.GetMessage(ctx, cred, mailbox, id)
+}
diff --git a/internal/imapclient/service_test.go b/internal/imapclient/service_test.go
new file mode 100644
index 0000000..21f4ac0
--- /dev/null
+++ b/internal/imapclient/service_test.go
@@ -0,0 +1,38 @@
+package imapclient
+
+import (
+	"context"
+	"testing"
+
+	"email-mcp/internal/secretstore"
+)
+
+type backendStub struct{}
+
+func (backendStub) ListMailboxes(context.Context, secretstore.Credential) ([]Mailbox, error) {
+	return []Mailbox{{Name: "INBOX"}}, nil
+}
+
+func (backendStub) ListMessages(context.Context, secretstore.Credential, string, int) ([]MessageSummary, error) {
+	return nil, nil
+}
+
+func (backendStub) GetMessage(context.Context, secretstore.Credential, string, string) (Message, error) {
+	return Message{}, nil
+}
+
+func TestServiceListMailboxesUsesBackend(t *testing.T) {
+	svc := NewService(backendStub{})
+
+	boxes, err := svc.ListMailboxes(context.Background(), secretstore.Credential{
+		Host:     "imap.example.com",
+		Username: "alice",
+		Password: "secret",
+	})
+	if err != nil {
+		t.Fatalf("ListMailboxes returned error: %v", err)
+	}
+	if len(boxes) != 1 || boxes[0].Name != "INBOX" {
+		t.Fatalf("unexpected mailboxes: %#v", boxes)
+	}
+}
diff --git a/internal/imapclient/types.go b/internal/imapclient/types.go
new file mode 100644
index 0000000..7184a4b
--- /dev/null
+++ b/internal/imapclient/types.go
@@ -0,0 +1,31 @@
+package imapclient
+
+import (
+	"context"
+
+	"email-mcp/internal/secretstore"
+)
+
+type Mailbox struct {
+	Name string `json:"name"`
+}
+
+type MessageSummary struct {
+	ID      string `json:"id"`
+	Subject string `json:"subject"`
+	From    string `json:"from"`
+	UID     uint32 `json:"uid"`
+}
+
+type Message struct {
+	ID      string            `json:"id"`
+	Mailbox string            `json:"mailbox"`
+	Headers map[string]string `json:"headers"`
+	Body    string            `json:"body"`
+}
+
+type Backend interface {
+	ListMailboxes(context.Context, secretstore.Credential) ([]Mailbox, error)
+	ListMessages(context.Context, secretstore.Credential, string, int) ([]MessageSummary, error)
+	GetMessage(context.Context, secretstore.Credential, string, string) (Message, error)
+}