added IMAP, LetsEncrypt, update layout

internal/imapserver/server.go

@@ -0,0 +1,33 @@
+package imapserver
+
+import (
+	"crypto/tls"
+
+	goimapserver "github.com/emersion/go-imap/v2/imapserver"
+)
+
+func newSessionFunc(backend *Backend) func(*goimapserver.Conn) (goimapserver.Session, *goimapserver.GreetingData, error) {
+	return func(c *goimapserver.Conn) (goimapserver.Session, *goimapserver.GreetingData, error) {
+		return backend.NewSession(), nil, nil
+	}
+}
+
+// NewPlainServer mirrors smtpserver.NewPlainServer: no TLS at all, so STARTTLS is
+// never offered. InsecureAuth is required here or LOGIN would always fail with
+// [PRIVACYREQUIRED] on this listener.
+func NewPlainServer(backend *Backend) *goimapserver.Server {
+	return goimapserver.New(&goimapserver.Options{
+		NewSession:   newSessionFunc(backend),
+		InsecureAuth: true,
+	})
+}
+
+// NewTLSServer mirrors smtpserver.NewTLSServer: implicit TLS, the whole connection is
+// encrypted from the first byte. Call ListenAndServeTLS (not ListenAndServe) to run
+// it — TLSConfig here only takes effect for that method.
+func NewTLSServer(backend *Backend, tlsConfig *tls.Config) *goimapserver.Server {
+	return goimapserver.New(&goimapserver.Options{
+		NewSession: newSessionFunc(backend),
+		TLSConfig:  tlsConfig,
+	})
+}