This is the v1 version, had the v2 before.

backend/backendutil/envelope.go

@@ -0,0 +1,58 @@
+package backendutil
+
+import (
+	"net/mail"
+	"strings"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message/textproto"
+)
+
+func headerAddressList(value string) ([]*imap.Address, error) {
+	addrs, err := mail.ParseAddressList(value)
+	if err != nil {
+		return []*imap.Address{}, err
+	}
+
+	list := make([]*imap.Address, len(addrs))
+	for i, a := range addrs {
+		parts := strings.SplitN(a.Address, "@", 2)
+		mailbox := parts[0]
+		var hostname string
+		if len(parts) == 2 {
+			hostname = parts[1]
+		}
+
+		list[i] = &imap.Address{
+			PersonalName: a.Name,
+			MailboxName:  mailbox,
+			HostName:     hostname,
+		}
+	}
+
+	return list, err
+}
+
+// FetchEnvelope returns a message's envelope from its header.
+func FetchEnvelope(h textproto.Header) (*imap.Envelope, error) {
+	env := new(imap.Envelope)
+
+	env.Date, _ = mail.ParseDate(h.Get("Date"))
+	env.Subject = h.Get("Subject")
+	env.From, _ = headerAddressList(h.Get("From"))
+	env.Sender, _ = headerAddressList(h.Get("Sender"))
+	if len(env.Sender) == 0 {
+		env.Sender = env.From
+	}
+	env.ReplyTo, _ = headerAddressList(h.Get("Reply-To"))
+	if len(env.ReplyTo) == 0 {
+		env.ReplyTo = env.From
+	}
+	env.To, _ = headerAddressList(h.Get("To"))
+	env.Cc, _ = headerAddressList(h.Get("Cc"))
+	env.Bcc, _ = headerAddressList(h.Get("Bcc"))
+	env.InReplyTo = h.Get("In-Reply-To")
+	env.MessageId = h.Get("Message-Id")
+
+	return env, nil
+}