diff --git a/go.mod b/go.mod
index 2b82cf3..4d6753b 100644
--- a/go.mod
+++ b/go.mod
@@ -6,13 +6,12 @@ require (
 	github.com/emersion/go-imap v1.0.0-beta.4
 	github.com/emersion/go-imap-move v0.0.0-20180601155324-5eb20cb834bf
 	github.com/emersion/go-imap-specialuse v0.0.0-20161227184202-ba031ced6a62
-	github.com/emersion/go-message v0.9.2
+	github.com/emersion/go-message v0.10.2
 	github.com/emersion/go-smtp v0.11.0
 	github.com/emersion/go-vcard v0.0.0-20190105225839-8856043f13c5
 	github.com/emersion/go-webdav v0.0.0-20180509190321-4ef680e9a32f
 	github.com/howeyc/gopass v0.0.0-20170109162249-bf9dde6d0d2c
-	golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529
-	golang.org/x/net v0.0.0-20190509222800-a4d6f7feada5 // indirect
-	golang.org/x/sys v0.0.0-20190509141414-a5b02f93d862 // indirect
-	golang.org/x/text v0.3.2 // indirect
+	golang.org/x/crypto v0.0.0-20190513172903-22d7a77e9e5f
+	golang.org/x/net v0.0.0-20190514140710-3ec191127204 // indirect
+	golang.org/x/sys v0.0.0-20190515120540-06a5c4944438 // indirect
 )
diff --git a/imap/mailbox.go b/imap/mailbox.go
index 98d8e30..5661352 100644
--- a/imap/mailbox.go
+++ b/imap/mailbox.go
@@ -315,9 +315,14 @@ func (mbox *mailbox) SearchMessages(isUID bool, c *imap.SearchCriteria) ([]uint3
 
 		h := messageHeader(msg)
 		for key, wantValues := range c.Header {
-			values, ok := h[key]
+			fields := h.FieldsByKey(key)
+			var values []string
+			for fields.Next() {
+				values = append(values, fields.Value())
+			}
+
 			for _, wantValue := range wantValues {
-				if wantValue == "" && !ok {
+				if wantValue == "" && len(values) == 0 {
 					return nil
 				}
 				if wantValue != "" {
diff --git a/imap/message.go b/imap/message.go
index 5044dfd..7a769b6 100644
--- a/imap/message.go
+++ b/imap/message.go
@@ -27,10 +27,9 @@ func messageID(msg *protonmail.Message) string {
 
 func formatHeader(h mail.Header) string {
 	var b bytes.Buffer
-	for k, values := range h.Header {
-		for _, v := range values {
-			b.WriteString(fmt.Sprintf("%s: %s\r\n", k, v))
-		}
+	fields := h.Fields()
+	for fields.Next() {
+		b.WriteString(fmt.Sprintf("%s: %s\r\n", fields.Key(), fields.Value()))
 	}
 	return b.String()
 }
@@ -195,7 +194,7 @@ func (mbox *mailbox) attachmentBody(att *protonmail.Attachment) (io.Reader, erro
 }
 
 func inlineHeader(msg *protonmail.Message) message.Header {
-	h := mail.NewTextHeader()
+	var h mail.InlineHeader
 	if msg.MIMEType != "" {
 		h.SetContentType(msg.MIMEType, nil)
 	} else {
@@ -206,7 +205,7 @@ func inlineHeader(msg *protonmail.Message) message.Header {
 }
 
 func attachmentHeader(att *protonmail.Attachment) message.Header {
-	h := mail.NewAttachmentHeader()
+	var h mail.AttachmentHeader
 	h.SetContentType(att.MIMEType, nil)
 	h.Set("Content-Transfer-Encoding", "base64")
 	h.SetFilename(att.Name)
@@ -232,7 +231,7 @@ func mailAddressList(addresses []*protonmail.MessageAddress) []*mail.Address {
 }
 
 func messageHeader(msg *protonmail.Message) message.Header {
-	h := mail.NewHeader()
+	var h mail.Header
 	h.SetContentType("multipart/mixed", nil)
 	h.SetDate(time.Unix(msg.Time, 0))
 	h.SetSubject(msg.Subject)
@@ -464,7 +463,7 @@ func createMessage(c *protonmail.Client, u *protonmail.User, privateKeys openpgp
 		}
 
 		switch h := p.Header.(type) {
-		case mail.TextHeader:
+		case *mail.InlineHeader:
 			t, _, err := h.ContentType()
 			if err != nil {
 				break
@@ -479,7 +478,7 @@ func createMessage(c *protonmail.Client, u *protonmail.User, privateKeys openpgp
 			if _, err := io.Copy(body, p.Body); err != nil {
 				return nil, err
 			}
-		case mail.AttachmentHeader:
+		case *mail.AttachmentHeader:
 			t, _, err := h.ContentType()
 			if err != nil {
 				break
diff --git a/smtp/smtp.go b/smtp/smtp.go
index 859d2d5..231fef3 100644
--- a/smtp/smtp.go
+++ b/smtp/smtp.go
@@ -29,10 +29,9 @@ func toPMAddressList(addresses []*mail.Address) []*protonmail.MessageAddress {
 
 func formatHeader(h mail.Header) string {
 	var b bytes.Buffer
-	for k, values := range h.Header {
-		for _, v := range values {
-			b.WriteString(fmt.Sprintf("%s: %s\r\n", k, v))
-		}
+	fields := h.Fields()
+	for fields.Next() {
+		b.WriteString(fmt.Sprintf("%s: %s\r\n", fields.Key(), fields.Value()))
 	}
 	return b.String()
 }
@@ -168,7 +167,7 @@ func (s *session) Data(r io.Reader) error {
 		}
 
 		switch h := p.Header.(type) {
-		case mail.TextHeader:
+		case *mail.InlineHeader:
 			t, _, err := h.ContentType()
 			if err != nil {
 				break
@@ -183,7 +182,7 @@ func (s *session) Data(r io.Reader) error {
 			if _, err := io.Copy(body, p.Body); err != nil {
 				return err
 			}
-		case mail.AttachmentHeader:
+		case *mail.AttachmentHeader:
 			t, _, err := h.ContentType()
 			if err != nil {
 				break