diff --git a/services/mail/mail-common/src/__tests__/mutex.test.ts b/services/mail/mail-common/src/__tests__/mutex.test.ts
index 66cf83cc6b..f491964a96 100644
--- a/services/mail/mail-common/src/__tests__/mutex.test.ts
+++ b/services/mail/mail-common/src/__tests__/mutex.test.ts
@@ -449,4 +449,320 @@ describe('SyncMutex', () => {
 
     expect(results).toEqual(['caught error', 'acquired lock', 'released lock'])
   })
+
+  it('should be resilient to unexpected errors during lock acquisition', async () => {
+    // Existing test...
+  })
+
+  it('should release locks when an error is thrown within a promise chain', async () => {
+    const lockKey = 'promise-error'
+    const executionOrder: string[] = []
+
+    // First lock with an error in the promise chain
+    try {
+      const promise = mutex.lock(lockKey).then((release) => {
+        executionOrder.push('lock1 acquired')
+
+        // Create a promise chain with an error
+        return Promise.resolve()
+          .then(() => {
+            executionOrder.push('lock1 processing')
+            throw new Error('Error in promise chain')
+          })
+          .finally(() => {
+            executionOrder.push('lock1 releasing')
+            release()
+          })
+      })
+
+      await promise
+      executionOrder.push('lock1 completed') // Should not reach here
+    } catch (error) {
+      executionOrder.push('error caught')
+    }
+
+    // Second lock should still work
+    const release2 = await mutex.lock(lockKey)
+    executionOrder.push('lock2 acquired')
+    release2()
+
+    expect(executionOrder).toEqual([
+      'lock1 acquired',
+      'lock1 processing',
+      'lock1 releasing',
+      'error caught',
+      'lock2 acquired'
+    ])
+  })
+
+  it('should handle async rejection with multiple lock requests', async () => {
+    const lockKey = 'async-rejection'
+    const results: string[] = []
+
+    // First task acquires the lock but fails
+    const failingTask = async (): Promise<void> => {
+      const release = await mutex.lock(lockKey)
+      try {
+        results.push('task1 started')
+        await new Promise((resolve) => setTimeout(resolve, 20))
+        throw new Error('Async task error')
+      } catch (error) {
+        results.push('task1 error caught')
+        throw error // Re-throw the error
+      } finally {
+        results.push('task1 releasing lock')
+        release()
+      }
+    }
+
+    // Second task waits for the lock
+    const waitingTask = async (): Promise<void> => {
+      results.push('task2 waiting')
+      const release = await mutex.lock(lockKey)
+      try {
+        results.push('task2 acquired lock')
+        await new Promise((resolve) => setTimeout(resolve, 10))
+        results.push('task2 completed')
+      } finally {
+        release()
+      }
+    }
+
+    // Run both tasks
+    try {
+      await failingTask()
+    } catch (error) {
+      results.push('outer catch')
+    }
+
+    await waitingTask()
+
+    // Verify error handling and lock release
+    expect(results).toEqual([
+      'task1 started',
+      'task1 error caught',
+      'task1 releasing lock',
+      'outer catch',
+      'task2 waiting',
+      'task2 acquired lock',
+      'task2 completed'
+    ])
+  })
+
+  it('should handle nested lock acquisitions with errors', async () => {
+    const outerKey = 'outer-lock'
+    const innerKey = 'inner-lock'
+    const results: string[] = []
+
+    // Function that acquires nested locks with an error in the middle
+    const nestedLocks = async (shouldFail: boolean): Promise<void> => {
+      const outerRelease = await mutex.lock(outerKey)
+      try {
+        results.push('outer lock acquired')
+
+        // Acquire inner lock
+        const innerRelease = await mutex.lock(innerKey)
+        try {
+          results.push('inner lock acquired')
+
+          // Simulate work that might fail
+          if (shouldFail) {
+            throw new Error('Error in nested locks')
+          }
+
+          results.push('work completed successfully')
+        } finally {
+          results.push('inner lock releasing')
+          innerRelease()
+        }
+      } catch (error) {
+        results.push('nested error caught')
+        throw error // Re-throw to test outer catch
+      } finally {
+        results.push('outer lock releasing')
+        outerRelease()
+      }
+    }
+
+    // First attempt - should fail
+    try {
+      await nestedLocks(true)
+    } catch (error) {
+      results.push('outer error handler')
+    }
+
+    // Second attempt - should succeed
+    await nestedLocks(false)
+
+    // Verify both locks were properly released during the error scenario
+    expect(results).toEqual([
+      'outer lock acquired',
+      'inner lock acquired',
+      'inner lock releasing',
+      'nested error caught',
+      'outer lock releasing',
+      'outer error handler',
+      'outer lock acquired',
+      'inner lock acquired',
+      'work completed successfully',
+      'inner lock releasing',
+      'outer lock releasing'
+    ])
+  })
+
+  it('should handle complex promise interactions with multiple rejections', async () => {
+    const lockKey = 'complex-promises'
+    const results: string[] = []
+
+    // Simulate a complex chain of promises with potential errors
+    const complexOperation = async (): Promise<void> => {
+      const release = await mutex.lock(lockKey)
+
+      try {
+        results.push('lock acquired')
+
+        // Create a promise that might reject
+        const operation = new Promise<string>((resolve, reject) => {
+          setTimeout(() => {
+            // Randomly decide to succeed or fail
+            if (Math.random() < 0.5) {
+              reject(new Error('Random operation failure'))
+            } else {
+              resolve('operation succeeded')
+            }
+          }, 10)
+        })
+
+        // Create a race condition
+        const result = await Promise.race([
+          operation,
+          // eslint-disable-next-line promise/param-names
+          new Promise<string>((_, reject) => {
+            setTimeout(() => {
+              reject(new Error('Timeout'))
+            }, 15)
+          })
+        ])
+
+        results.push(result)
+      } catch (error: any) {
+        results.push(`error: ${error.message}`)
+      } finally {
+        results.push('lock released')
+        release()
+      }
+    }
+
+    // Run multiple operations in parallel
+    await Promise.all([complexOperation(), complexOperation(), complexOperation()])
+
+    // Each operation should have 3 log entries: acquired, result/error, released
+    expect(results.length).toBe(9)
+
+    // Group the results in sets of 3
+    const operations = [results.slice(0, 3), results.slice(3, 6), results.slice(6, 9)]
+
+    // Each operation should follow the pattern: acquired -> result/error -> released
+    operations.forEach((op) => {
+      expect(op[0]).toBe('lock acquired')
+      expect(op[2]).toBe('lock released')
+      // Middle entry should be either the result or an error
+      expect(op[1]).toMatch(/^(operation succeeded|error: .*)/)
+    })
+  })
+
+  it('should handle rejections in async/await expressions within lock', async () => {
+    const lockKey = 'async-await-rejection'
+    const executionOrder: string[] = []
+
+    // Function that will throw within an async/await expression
+    const asyncFunction = async (): Promise<void> => {
+      const release = await mutex.lock(lockKey)
+      try {
+        executionOrder.push('lock acquired')
+
+        // Nested async operation that fails
+        const nestedOperation = async (): Promise<string> => {
+          await new Promise((resolve) => setTimeout(resolve, 10))
+          throw new Error('Nested operation failed')
+        }
+
+        // This should throw
+        const result = await nestedOperation()
+        executionOrder.push(`got result: ${result}`) // Should not be reached
+      } catch (error) {
+        executionOrder.push('caught nested error')
+      } finally {
+        executionOrder.push('releasing lock')
+        release()
+      }
+    }
+
+    await asyncFunction()
+
+    // Another lock on the same key should work
+    const secondOp = async (): Promise<void> => {
+      const release = await mutex.lock(lockKey)
+      try {
+        executionOrder.push('second lock acquired')
+      } finally {
+        release()
+      }
+    }
+
+    await secondOp()
+
+    expect(executionOrder).toEqual(['lock acquired', 'caught nested error', 'releasing lock', 'second lock acquired'])
+  })
+
+  it('should handle errors thrown in finally blocks within lock', async () => {
+    const lockKey = 'finally-error'
+    const executionOrder: string[] = []
+
+    // Function that will throw in a finally block
+    const problematicFunction = async (): Promise<void> => {
+      const release = await mutex.lock(lockKey)
+      try {
+        executionOrder.push('lock acquired')
+        throw new Error('Initial error')
+      } catch (error) {
+        executionOrder.push('caught initial error')
+      } finally {
+        executionOrder.push('in finally block')
+
+        // This is bad practice but we need to test it works
+        try {
+          // Throw in finally - could suppress the original error if not caught
+          // eslint-disable-next-line no-unsafe-finally
+          throw new Error('Error in finally')
+        } catch (finallyError) {
+          executionOrder.push('caught finally error')
+        }
+
+        // Still need to release the lock
+        release()
+        executionOrder.push('lock released')
+      }
+    }
+
+    await problematicFunction()
+
+    // Verify we can still get the lock
+    const secondOp = async (): Promise<void> => {
+      const release = await mutex.lock(lockKey)
+      executionOrder.push('second lock acquired')
+      release()
+    }
+
+    await secondOp()
+
+    expect(executionOrder).toEqual([
+      'lock acquired',
+      'caught initial error',
+      'in finally block',
+      'caught finally error',
+      'lock released',
+      'second lock acquired'
+    ])
+  })
 })
diff --git a/services/mail/mail-common/src/mutex.ts b/services/mail/mail-common/src/mutex.ts
index 246154a04b..3aa4d14e00 100644
--- a/services/mail/mail-common/src/mutex.ts
+++ b/services/mail/mail-common/src/mutex.ts
@@ -12,9 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
+
+interface LockRequest {
+  promise: Promise<void>
+  resolve: () => void
+}
 export class SyncMutex {
   // Queue of pending promises for each lock key
-  private readonly locks = new Map<string, Array<{ promise: Promise<void>, resolve: () => void }>>()
+  private readonly locks = new Map<string, Array<LockRequest>>()
 
   async lock (key: string): Promise<() => void> {
     // Initialize queue if it doesn't exist
@@ -22,7 +27,7 @@ export class SyncMutex {
       this.locks.set(key, [])
     }
 
-    const queue = this.locks.get(key) ?? []
+    const queue = this.locks.get(key) as Array<LockRequest>
 
     // Create a new lock request
     let releaseFn!: () => void
@@ -44,11 +49,7 @@ export class SyncMutex {
 
         // If there are more locks in the queue, resolve the next one
         if (queue.length > 0) {
-          try {
-            queue[0].resolve()
-          } catch (error) {
-            console.error(`Error resolving next lock in queue for key "${key}":`, error)
-          }
+          queue[0].resolve()
         }
 
         // If queue is empty, clean up
@@ -56,11 +57,7 @@ export class SyncMutex {
           this.locks.delete(key)
         }
 
-        try {
-          resolve()
-        } catch (error) {
-          console.error(`Error resolving lock release for key "${key}":`, error)
-        }
+        resolve()
       }
     })