diff --git a/dev/Model/Identity.js b/dev/Model/Identity.js
index ac46a15fe..89beda875 100644
--- a/dev/Model/Identity.js
+++ b/dev/Model/Identity.js
@@ -32,9 +32,9 @@ export class IdentityModel extends AbstractModel {
 		});
 
 		addComputablesTo(this, {
-			smimeKeyEncrypted: () => this.smimeKey().includes('-----BEGIN ENCRYPTED PRIVATE KEY-----')
-//			smimeKeyValid: () => this.smimeKeyEncrypted() | this.smimeKey().includes('-----BEGIN PRIVATE KEY-----')
-//			smimeCertificateValid: () => this.smimeKey().includes('-----BEGIN CERTIFICATE-----')
+			smimeKeyEncrypted: () => this.smimeKey().includes('-----BEGIN ENCRYPTED PRIVATE KEY-----'),
+			smimeKeyValid: () => /^-----BEGIN (ENCRYPTED )?PRIVATE KEY-----/.test(this.smimeKey()),
+			smimeCertificateValid: () => /^-----BEGIN CERTIFICATE-----/.test(this.smimeCertificate())
 		});
 	}
 
diff --git a/dev/View/Popup/Compose.js b/dev/View/Popup/Compose.js
index 2fd0e23bd..4384c5b25 100644
--- a/dev/View/Popup/Compose.js
+++ b/dev/View/Popup/Compose.js
@@ -1377,7 +1377,7 @@ export class ComposePopupView extends AbstractViewPopup {
 		key && options.push(['OpenPGP', key]);
 		key = GnuPGUserStore.getPrivateKeyFor(email, 1);
 		key && options.push(['GnuPG', key]);
-		identity.smimeKey() && identity.smimeCertificate() && identity.email() === email
+		identity.smimeKeyValid() && identity.smimeCertificateValid() && identity.email() === email
 			&& options.push(['S/MIME']);
 		console.dir({signOptions: options});
 		this.signOptions(options);
diff --git a/snappymail/v/0.0.0/app/templates/Views/User/PopupsIdentity.html b/snappymail/v/0.0.0/app/templates/Views/User/PopupsIdentity.html
index 57c451116..2f7934fdc 100644
--- a/snappymail/v/0.0.0/app/templates/Views/User/PopupsIdentity.html
+++ b/snappymail/v/0.0.0/app/templates/Views/User/PopupsIdentity.html
@@ -88,11 +88,11 @@
 -->
 			<details>
 				<summary><strong>S/MIME</strong></summary>
-				<div class="control-group">
+				<div class="control-group" data-bind="css: {'error': smimeKey() && !smimeKeyValid()}">
 					<label data-i18n="CRYPTO/PRIVATE_KEY"></label>
 					<textarea name="smimeKey" class="input-xxlarge" rows="14" autofocus="" autocomplete="off" data-bind="value: smimeKey"></textarea>
 				</div>
-				<div class="control-group">
+				<div class="control-group" data-bind="css: {'error': smimeCertificate() && !smimeCertificateValid()}">
 					<label data-i18n="SMIME/CERTIFICATE"></label>
 					<textarea name="smimeCertificate" class="input-xxlarge" rows="14" autofocus="" autocomplete="off" data-bind="value: smimeCertificate"></textarea>
 				</div>