diff --git a/lib/reducers/calendar-filters-reducer.js b/lib/reducers/calendar-filters-reducer.js
--- a/lib/reducers/calendar-filters-reducer.js
+++ b/lib/reducers/calendar-filters-reducer.js
@@ -42,7 +42,10 @@
   type ClientUpdateInfo,
   processUpdatesActionType,
 } from '../types/update-types.js';
-import { setNewSessionActionType } from '../utils/action-utils.js';
+import {
+  extractKeyserverIDFromID,
+  setNewSessionActionType,
+} from '../utils/action-utils.js';
 import { filterThreadIDsBelongingToCommunity } from '../utils/drawer-utils.react.js';
 
 export default function reduceCalendarFilters(
@@ -156,17 +159,16 @@
   return state;
 }
 
-function removeDeletedThreadIDsFromFilterList(
+function filterThreadIDsInFilterList(
   state: $ReadOnlyArray<CalendarFilter>,
-  threadInfos: RawThreadInfos,
+  filterCondition: (threadID: string) => boolean,
 ): $ReadOnlyArray<CalendarFilter> {
   const currentlyFilteredIDs = filteredThreadIDs(state);
   if (!currentlyFilteredIDs) {
     return state;
   }
-  const filtered = [...currentlyFilteredIDs].filter(threadID =>
-    threadInFilterList(threadInfos[threadID]),
-  );
+  const filtered = [...currentlyFilteredIDs].filter(filterCondition);
+
   if (filtered.length < currentlyFilteredIDs.size) {
     return [
       ...nonThreadCalendarFilters(state),
@@ -175,3 +177,29 @@
   }
   return state;
 }
+
+function removeDeletedThreadIDsFromFilterList(
+  state: $ReadOnlyArray<CalendarFilter>,
+  threadInfos: RawThreadInfos,
+): $ReadOnlyArray<CalendarFilter> {
+  const filterCondition = (threadID: string) =>
+    threadInFilterList(threadInfos[threadID]);
+
+  return filterThreadIDsInFilterList(state, filterCondition);
+}
+
+function removeKeyserverThreadIDsFromFilterList(
+  state: $ReadOnlyArray<CalendarFilter>,
+  keyserverIDs: $ReadOnlyArray<string>,
+): $ReadOnlyArray<CalendarFilter> {
+  const keyserverIDsSet = new Set<string>(keyserverIDs);
+  const filterCondition = (threadID: string) =>
+    !keyserverIDsSet.has(extractKeyserverIDFromID(threadID));
+
+  return filterThreadIDsInFilterList(state, filterCondition);
+}
+
+export {
+  removeDeletedThreadIDsFromFilterList,
+  removeKeyserverThreadIDsFromFilterList,
+};
diff --git a/lib/reducers/calendar-filters-reducer.test.js b/lib/reducers/calendar-filters-reducer.test.js
new file mode 100644
--- /dev/null
+++ b/lib/reducers/calendar-filters-reducer.test.js
@@ -0,0 +1,173 @@
+// @flow
+
+import {
+  removeDeletedThreadIDsFromFilterList,
+  removeKeyserverThreadIDsFromFilterList,
+} from './calendar-filters-reducer.js';
+import type { ThreadStore } from '../types/thread-types';
+
+const calendarFilters = [
+  { type: 'threads', threadIDs: ['256|1', '256|83815'] },
+];
+
+const threadStore: ThreadStore = {
+  threadInfos: {
+    '256|1': {
+      id: '256|1',
+      type: 12,
+      name: 'GENESIS',
+      description: '',
+      color: '648caa',
+      creationTime: 1689091732528,
+      parentThreadID: null,
+      repliesCount: 0,
+      containingThreadID: null,
+      community: null,
+      pinnedCount: 0,
+      minimallyEncoded: true,
+      members: [
+        {
+          id: '256',
+          role: '256|83796',
+          permissions: '3f73ff',
+          isSender: true,
+          minimallyEncoded: true,
+        },
+        {
+          id: '83810',
+          role: '256|83795',
+          permissions: '3',
+          isSender: false,
+          minimallyEncoded: true,
+        },
+      ],
+      roles: {
+        '256|83795': {
+          id: '256|83795',
+          name: 'Members',
+          permissions: ['000', '010', '005', '015', '0a7'],
+          isDefault: true,
+          minimallyEncoded: true,
+        },
+        '256|83796': {
+          id: '256|83796',
+          name: 'Admins',
+          permissions: ['000', '010', '005', '015', '0a7'],
+          isDefault: false,
+          minimallyEncoded: true,
+        },
+      },
+      currentUser: {
+        role: '256|83795',
+        permissions: '3',
+        subscription: {
+          home: true,
+          pushNotifs: true,
+        },
+        unread: false,
+        minimallyEncoded: true,
+      },
+    },
+    '256|83815': {
+      id: '256|83815',
+      type: 7,
+      name: '',
+      description:
+        'This is your private chat, where you can set reminders and jot notes in private!',
+      color: '57697f',
+      creationTime: 1689248242797,
+      parentThreadID: '256|1',
+      repliesCount: 0,
+      containingThreadID: '256|1',
+      community: '256|1',
+      pinnedCount: 0,
+      minimallyEncoded: true,
+      members: [
+        {
+          id: '256',
+          role: null,
+          permissions: '2c7fff',
+          isSender: false,
+          minimallyEncoded: true,
+        },
+        {
+          id: '83810',
+          role: '256|83816',
+          permissions: '3026f',
+          isSender: true,
+          minimallyEncoded: true,
+        },
+      ],
+      roles: {
+        '256|83816': {
+          id: '256|83816',
+          name: 'Members',
+          permissions: ['000', '010', '005', '015', '0a7'],
+          isDefault: true,
+          minimallyEncoded: true,
+        },
+      },
+      currentUser: {
+        role: null,
+        permissions: '3026f',
+        subscription: {
+          home: true,
+          pushNotifs: true,
+        },
+        unread: false,
+        minimallyEncoded: true,
+      },
+    },
+  },
+};
+
+describe('removeDeletedThreadIDsFromFilterList', () => {
+  it('Removes threads the user is not a member of anymore', () => {
+    expect(
+      removeDeletedThreadIDsFromFilterList(
+        calendarFilters,
+        threadStore.threadInfos,
+      ),
+    ).toEqual([{ type: 'threads', threadIDs: ['256|1'] }]);
+  });
+});
+
+const threadIDsToStay = [
+  '256|1',
+  '256|2',
+  '200|4',
+  '300|5',
+  '300|6',
+  '256|100',
+];
+const threadToRemove1 = '100';
+const threadToRemove2 = '400';
+const threadIDsToRemove = [
+  threadToRemove1 + '|3',
+  threadToRemove1 + '|7',
+  threadToRemove2 + '|8',
+];
+const calendarFiltersState = [
+  { type: 'not_deleted' },
+  {
+    type: 'threads',
+    threadIDs: [...threadIDsToStay, ...threadIDsToRemove],
+  },
+];
+
+describe('removeKeyserverThreadIDsFromFilterList', () => {
+  it('Removes threads from the given keyserver', () => {
+    expect(
+      removeKeyserverThreadIDsFromFilterList(calendarFiltersState, [
+        threadToRemove1,
+        threadToRemove2,
+      ]),
+    ).toEqual([
+      { type: 'not_deleted' },
+      {
+        type: 'threads',
+        threadIDs: threadIDsToStay,
+      },
+    ]);
+  });
+});