diff --git a/backend/src/lib/api.ts b/backend/src/lib/api.ts
index df87ca6..f79424b 100644
--- a/backend/src/lib/api.ts
+++ b/backend/src/lib/api.ts
@@ -155,21 +155,40 @@ app.post("/login/step/username", async (req, res) => {
       });
       req.session.login.session_id = session.id;
 
-      await deliveryProvider!.send([username, instance], "code: " + code);
+      try {
+        await deliveryProvider!.send([username, instance], "code: " + code);
 
-      req.session.save(() => {
-        res.send({
-          success: true,
-          step: "CODE_SENT",
-          data: {
-            session_id: session.id,
-            account:
-              deliveryProvider!.service_account.username +
-              "@" +
-              deliveryProvider!.service_account.host,
-          },
+        req.session.save(() => {
+          res.send({
+            success: true,
+            step: "CODE_SENT",
+            data: {
+              session_id: session.id,
+              account:
+                deliveryProvider!.service_account.username +
+                "@" +
+                deliveryProvider!.service_account.host,
+            },
+          });
         });
-      });
+      } catch (e) {
+        console.error(
+          "Error while delivering to " + [username, instance].join("@"),
+          e
+        );
+
+        await prisma.authSession.delete({ where: { id: session.id } });
+        req.session.login.session_id = undefined;
+
+        req.session.save(() => {
+          res.send({
+            success: false,
+            error:
+              "Error while sending: " +
+              ((e as any)?.message || "unknown error"),
+          });
+        });
+      }
 
       break;
     }
diff --git a/backend/src/lib/express.ts b/backend/src/lib/express.ts
index 62da7e9..4b4bd54 100644
--- a/backend/src/lib/express.ts
+++ b/backend/src/lib/express.ts
@@ -5,6 +5,7 @@ import bodyParser from "body-parser";
 import path from "path";
 import { oidc } from "./oidc.js";
 import { makeClientPublic } from "./utils.js";
+import { errors as OIDC_Errors } from "oidc-provider";
 
 import "../types/session-types.js";
 import { APIRouter } from "./api.js";
@@ -44,13 +45,25 @@ app.use("/interaction/:uid", async (req, res, next) => {
     if (typeof req.session.user === "undefined") {
       res.redirect("/login?return=" + encodeURIComponent(req.originalUrl));
     } else {
-      const returnTo = await oidc.interactionResult(req, res, {
-        login: { accountId: req.session.user.sub },
-      });
+      try {
+        const returnTo = await oidc.interactionResult(req, res, {
+          login: { accountId: req.session.user.sub },
+        });
 
-      req.session.destroy(() => {
-        res.redirect(returnTo);
-      });
+        req.session.destroy(() => {
+          res.redirect(returnTo);
+        });
+      } catch (e) {
+        console.error("Error while in interaction middleware", e);
+
+        req.session.destroy(() => {
+          if (e instanceof OIDC_Errors.SessionNotFound) {
+            res.send("<h1>session lost</h1>try logging in again");
+          } else {
+            res.send("<h1>unknown error</h1> try logging in again");
+          }
+        });
+      }
     }
 
     return;