diff --git a/mailhog/config/config.go b/mailhog/config/config.go
index a94a372..51401a3 100644
--- a/mailhog/config/config.go
+++ b/mailhog/config/config.go
@@ -1,5 +1,9 @@
 package config
 
+import (
+	"github.com/ian-kent/Go-MailHog/mailhog/storage"
+)
+
 func DefaultConfig() *Config {
 	return &Config{
 		SMTPBindAddr: "0.0.0.0:1025",
@@ -19,6 +23,6 @@ type Config struct {
 	MongoDb      string
 	MongoColl    string
 	MessageChan  chan interface{}
-	Storage      interface{}
+	Storage      storage.Storage
 	Assets       func(asset string) ([]byte, error)
 }
diff --git a/mailhog/smtp/protocol/protocol.go b/mailhog/smtp/protocol/protocol.go
index 980c8ce..7152713 100644
--- a/mailhog/smtp/protocol/protocol.go
+++ b/mailhog/smtp/protocol/protocol.go
@@ -23,10 +23,22 @@ type Protocol struct {
 	message  *data.SMTPMessage
 	hostname string
 
-	LogHandler                    func(message string, args ...interface{})
-	MessageReceivedHandler        func(*data.Message) (string, error)
-	ValidateSenderHandler         func(from string) bool
-	ValidateRecipientHandler      func(to string) bool
+	// LogHandler is called for each log message. If nil, log messages will
+	// be output using fmt.Printf instead.
+	LogHandler func(message string, args ...interface{})
+	// MessageReceivedHandler is called for each message accepted by the
+	// SMTP protocol. It must return a MessageID or error. If nil, messages
+	// will be rejected with an error.
+	MessageReceivedHandler func(*data.Message) (string, error)
+	// ValidateSenderHandler should return true if the sender is valid,
+	// otherwise false. If nil, all senders will be accepted.
+	ValidateSenderHandler func(from string) bool
+	// ValidateRecipientHandler should return true if the recipient is valid,
+	// otherwise false. If nil, all recipients will be accepted.
+	ValidateRecipientHandler func(to string) bool
+	// ValidateAuthenticationhandler should return true if the authentication
+	// parameters are valid, otherwise false. If nil, all authentication
+	// attempts will be accepted.
 	ValidateAuthenticationHandler func(mechanism string, args ...string) bool
 }
 
@@ -50,7 +62,8 @@ func (proto *Protocol) logf(message string, args ...interface{}) {
 	}
 }
 
-// Start begins an SMTP conversation with a 220 reply
+// Start begins an SMTP conversation with a 220 reply, placing the state
+// machine in ESTABLISH state.
 func (proto *Protocol) Start(hostname string) *Reply {
 	proto.state = ESTABLISH
 	proto.hostname = hostname
@@ -60,7 +73,8 @@ func (proto *Protocol) Start(hostname string) *Reply {
 // Parse parses a line string and returns any remaining line string
 // and a reply, if a command was found. Parse does nothing until a
 // new line is found.
-// - TODO move this to a buffer inside proto?
+// - TODO decide whether to move this to a buffer inside Protocol
+//   sort of like it this way, since it gives control back to the caller
 func (proto *Protocol) Parse(line string) (string, *Reply) {
 	var reply *Reply
 
@@ -266,7 +280,7 @@ func ParseMAIL(mail string) (string, error) {
 	r := regexp.MustCompile("(?i:From):<([^>]+)>")
 	match := r.FindStringSubmatch(mail)
 	if len(match) != 2 {
-		return "", errors.New("Invalid sender")
+		return "", errors.New("Invalid sender " + mail)
 	}
 	return match[1], nil
 }
@@ -276,7 +290,7 @@ func ParseRCPT(rcpt string) (string, error) {
 	r := regexp.MustCompile("(?i:To):<([^>]+)>")
 	match := r.FindStringSubmatch(rcpt)
 	if len(match) != 2 {
-		return "", errors.New("Invalid recipient")
+		return "", errors.New("Invalid recipient " + rcpt)
 	}
 	return match[1], nil
 }
diff --git a/mailhog/smtp/protocol/state.go b/mailhog/smtp/protocol/state.go
index cbb98e7..8c7dc0e 100644
--- a/mailhog/smtp/protocol/state.go
+++ b/mailhog/smtp/protocol/state.go
@@ -1,7 +1,5 @@
 package protocol
 
-// http://www.rfc-editor.org/rfc/rfc5321.txt
-
 // State represents the state of an SMTP conversation
 type State int
 
diff --git a/mailhog/smtp/server/session.go b/mailhog/smtp/server/session.go
index 72e49c0..6418102 100644
--- a/mailhog/smtp/server/session.go
+++ b/mailhog/smtp/server/session.go
@@ -3,7 +3,6 @@ package server
 // http://www.rfc-editor.org/rfc/rfc5321.txt
 
 import (
-	"errors"
 	"log"
 	"net"
 	"strings"
@@ -11,7 +10,6 @@ import (
 	"github.com/ian-kent/Go-MailHog/mailhog/config"
 	"github.com/ian-kent/Go-MailHog/mailhog/data"
 	"github.com/ian-kent/Go-MailHog/mailhog/smtp/protocol"
-	"github.com/ian-kent/Go-MailHog/mailhog/storage"
 )
 
 // Session represents a SMTP session using net.TCPConn
@@ -43,6 +41,7 @@ func Accept(conn *net.TCPConn, conf *config.Config) {
 func (c *Session) validateAuthentication(mechanism string, args ...string) bool {
 	return true
 }
+
 func (c *Session) validateRecipient(to string) bool {
 	return true
 }
@@ -52,16 +51,8 @@ func (c *Session) validateSender(from string) bool {
 }
 
 func (c *Session) acceptMessage(msg *data.Message) (id string, err error) {
-	switch c.conf.Storage.(type) {
-	case *storage.MongoDB:
-		c.logf("Storing message using MongoDB")
-		id, err = c.conf.Storage.(*storage.MongoDB).Store(msg)
-	case *storage.InMemory:
-		c.logf("Storing message using Memory")
-		id, err = c.conf.Storage.(*storage.InMemory).Store(msg)
-	default:
-		err = errors.New("Unknown storage stype")
-	}
+	c.logf("Storing message %s", msg.ID)
+	id, err = c.conf.Storage.Store(msg)
 	c.conf.MessageChan <- msg
 	return
 }
diff --git a/mailhog/storage/memory.go b/mailhog/storage/memory.go
index 6af3c39..eb297d8 100644
--- a/mailhog/storage/memory.go
+++ b/mailhog/storage/memory.go
@@ -1,22 +1,17 @@
 package storage
 
-import (
-	"github.com/ian-kent/Go-MailHog/mailhog/config"
-	"github.com/ian-kent/Go-MailHog/mailhog/data"
-)
+import "github.com/ian-kent/Go-MailHog/mailhog/data"
 
 // InMemory is an in memory storage backend
 type InMemory struct {
-	Config        *config.Config
 	Messages      map[string]*data.Message
 	MessageIndex  []string
 	MessageRIndex map[string]int
 }
 
 // CreateInMemory creates a new in memory storage backend
-func CreateInMemory(c *config.Config) *InMemory {
+func CreateInMemory() *InMemory {
 	return &InMemory{
-		Config:        c,
 		Messages:      make(map[string]*data.Message, 0),
 		MessageIndex:  make([]string, 0),
 		MessageRIndex: make(map[string]int, 0),
@@ -32,15 +27,16 @@ func (memory *InMemory) Store(m *data.Message) (string, error) {
 }
 
 // List lists stored messages by index
-func (memory *InMemory) List(start int, limit int) ([]*data.Message, error) {
+func (memory *InMemory) List(start int, limit int) (*data.Messages, error) {
 	if limit > len(memory.MessageIndex) {
 		limit = len(memory.MessageIndex)
 	}
-	var messages []*data.Message
+	var messages []data.Message
 	for _, m := range memory.MessageIndex[start:limit] {
-		messages = append(messages, memory.Messages[m])
+		messages = append(messages, *memory.Messages[m])
 	}
-	return messages, nil
+	msgs := data.Messages(messages)
+	return &msgs, nil
 }
 
 // DeleteOne deletes an individual message by storage ID
diff --git a/mailhog/storage/mongodb.go b/mailhog/storage/mongodb.go
index fe3fe71..3198342 100644
--- a/mailhog/storage/mongodb.go
+++ b/mailhog/storage/mongodb.go
@@ -3,7 +3,6 @@ package storage
 import (
 	"log"
 
-	"github.com/ian-kent/Go-MailHog/mailhog/config"
 	"github.com/ian-kent/Go-MailHog/mailhog/data"
 	"labix.org/v2/mgo"
 	"labix.org/v2/mgo/bson"
@@ -12,22 +11,20 @@ import (
 // MongoDB represents MongoDB backed storage backend
 type MongoDB struct {
 	Session    *mgo.Session
-	Config     *config.Config
 	Collection *mgo.Collection
 }
 
 // CreateMongoDB creates a MongoDB backed storage backend
-func CreateMongoDB(c *config.Config) *MongoDB {
-	log.Printf("Connecting to MongoDB: %s\n", c.MongoUri)
-	session, err := mgo.Dial(c.MongoUri)
+func CreateMongoDB(uri, db, coll string) *MongoDB {
+	log.Printf("Connecting to MongoDB: %s\n", uri)
+	session, err := mgo.Dial(uri)
 	if err != nil {
 		log.Printf("Error connecting to MongoDB: %s", err)
 		return nil
 	}
 	return &MongoDB{
 		Session:    session,
-		Config:     c,
-		Collection: session.DB(c.MongoDb).C(c.MongoColl),
+		Collection: session.DB(db).C(coll),
 	}
 }
 
diff --git a/mailhog/storage/storage.go b/mailhog/storage/storage.go
new file mode 100644
index 0000000..abb422b
--- /dev/null
+++ b/mailhog/storage/storage.go
@@ -0,0 +1,12 @@
+package storage
+
+import "github.com/ian-kent/Go-MailHog/mailhog/data"
+
+// Storage represents a storage backend
+type Storage interface {
+	Store(m *data.Message) (string, error)
+	List(start int, limit int) (*data.Messages, error)
+	DeleteOne(id string) error
+	DeleteAll() error
+	Load(id string) (*data.Message, error)
+}
diff --git a/main.go b/main.go
index dcb5e6e..c42d772 100644
--- a/main.go
+++ b/main.go
@@ -46,17 +46,17 @@ func configure() {
 
 	if storage_type == "mongodb" {
 		log.Println("Using MongoDB message storage")
-		s := storage.CreateMongoDB(conf)
+		s := storage.CreateMongoDB(conf.MongoUri, conf.MongoDb, conf.MongoColl)
 		if s == nil {
 			log.Println("MongoDB storage unavailable, reverting to in-memory storage")
-			conf.Storage = storage.CreateInMemory(conf)
+			conf.Storage = storage.CreateInMemory()
 		} else {
 			log.Println("Connected to MongoDB")
 			conf.Storage = s
 		}
 	} else if storage_type == "memory" {
 		log.Println("Using in-memory message storage")
-		conf.Storage = storage.CreateInMemory(conf)
+		conf.Storage = storage.CreateInMemory()
 	} else {
 		log.Fatalf("Invalid storage type %s", storage_type)
 	}