diff --git a/Source/Core/Core/DSP/DSPCore.cpp b/Source/Core/Core/DSP/DSPCore.cpp
index d06c324118..45e7cdfe8a 100644
--- a/Source/Core/Core/DSP/DSPCore.cpp
+++ b/Source/Core/Core/DSP/DSPCore.cpp
@@ -387,8 +387,8 @@ void SDSP::DoState(PointerWrap& p)
   p.Do(step_counter);
   p.DoArray(ifx_regs);
   accelerator->DoState(p);
-  p.Do(mbox[0]);
-  p.Do(mbox[1]);
+  p.Do(m_mailbox[0]);
+  p.Do(m_mailbox[1]);
   Common::UnWriteProtectMemory(iram, DSP_IRAM_BYTE_SIZE, false);
   p.DoArray(iram, DSP_IRAM_SIZE);
   Common::WriteProtectMemory(iram, DSP_IRAM_BYTE_SIZE, false);
diff --git a/Source/Core/Core/DSP/DSPCore.h b/Source/Core/Core/DSP/DSPCore.h
index fb8af13e38..60b317eecf 100644
--- a/Source/Core/Core/DSP/DSPCore.h
+++ b/Source/Core/Core/DSP/DSPCore.h
@@ -228,10 +228,10 @@ enum class ExceptionType
   ExternalInterrupt = 7     // 0x000e external int (message from CPU)
 };
 
-enum Mailbox : int
+enum class Mailbox
 {
-  MAILBOX_CPU,
-  MAILBOX_DSP
+  CPU,
+  DSP
 };
 
 struct DSP_Regs
@@ -429,9 +429,6 @@ struct SDSP
   u32 iram_crc = 0;
   u64 step_counter = 0;
 
-  // Mailbox.
-  std::atomic<u32> mbox[2];
-
   // Accelerator / DMA / other hardware registers. Not GPRs.
   std::array<u16, 256> ifx_regs{};
 
@@ -445,6 +442,9 @@ struct SDSP
   u16* coef = nullptr;
 
 private:
+  auto& GetMailbox(Mailbox mailbox) { return m_mailbox[static_cast<u32>(mailbox)]; }
+  const auto& GetMailbox(Mailbox mailbox) const { return m_mailbox[static_cast<u32>(mailbox)]; }
+
   void FreeMemoryPages();
 
   void DoDMA();
@@ -455,6 +455,7 @@ private:
 
   u16 ReadIFXImpl(u16 address);
 
+  std::array<std::atomic<u32>, 2> m_mailbox;
   DSPCore& m_dsp_core;
   Analyzer m_analyzer;
 };
diff --git a/Source/Core/Core/DSP/DSPHWInterface.cpp b/Source/Core/Core/DSP/DSPHWInterface.cpp
index 0733cc4e22..1b9cb2fe99 100644
--- a/Source/Core/Core/DSP/DSPHWInterface.cpp
+++ b/Source/Core/Core/DSP/DSPHWInterface.cpp
@@ -25,21 +25,21 @@ void SDSP::InitializeIFX()
 {
   ifx_regs.fill(0);
 
-  mbox[MAILBOX_CPU].store(0);
-  mbox[MAILBOX_DSP].store(0);
+  GetMailbox(Mailbox::CPU).store(0);
+  GetMailbox(Mailbox::DSP).store(0);
 }
 
 u32 SDSP::PeekMailbox(Mailbox mailbox) const
 {
-  return mbox[mailbox].load();
+  return GetMailbox(mailbox).load();
 }
 
 u16 SDSP::ReadMailboxLow(Mailbox mailbox)
 {
-  const u32 value = mbox[mailbox].load(std::memory_order_acquire);
-  mbox[mailbox].store(value & ~0x80000000, std::memory_order_release);
+  const u32 value = GetMailbox(mailbox).load(std::memory_order_acquire);
+  GetMailbox(mailbox).store(value & ~0x80000000, std::memory_order_release);
 
-  if (m_dsp_core.GetInitHax() && mailbox == MAILBOX_DSP)
+  if (m_dsp_core.GetInitHax() && mailbox == Mailbox::DSP)
   {
     m_dsp_core.SetInitHax(false);
     m_dsp_core.Reset();
@@ -47,7 +47,7 @@ u16 SDSP::ReadMailboxLow(Mailbox mailbox)
   }
 
 #if defined(_DEBUG) || defined(DEBUGFAST)
-  const char* const type = mailbox == MAILBOX_DSP ? "DSP" : "CPU";
+  const char* const type = mailbox == Mailbox::DSP ? "DSP" : "CPU";
   DEBUG_LOG_FMT(DSP_MAIL, "{}(RM) B:{} M:0x{:#010x} (pc={:#06x})", type, mailbox,
                 PeekMailbox(mailbox), pc);
 #endif
@@ -57,7 +57,7 @@ u16 SDSP::ReadMailboxLow(Mailbox mailbox)
 
 u16 SDSP::ReadMailboxHigh(Mailbox mailbox)
 {
-  if (m_dsp_core.GetInitHax() && mailbox == MAILBOX_DSP)
+  if (m_dsp_core.GetInitHax() && mailbox == Mailbox::DSP)
   {
     return 0x8054;
   }
@@ -68,13 +68,13 @@ u16 SDSP::ReadMailboxHigh(Mailbox mailbox)
 
 void SDSP::WriteMailboxLow(Mailbox mailbox, u16 value)
 {
-  const u32 old_value = mbox[mailbox].load(std::memory_order_acquire);
+  const u32 old_value = GetMailbox(mailbox).load(std::memory_order_acquire);
   const u32 new_value = (old_value & ~0xffff) | value;
 
-  mbox[mailbox].store(new_value | 0x80000000, std::memory_order_release);
+  GetMailbox(mailbox).store(new_value | 0x80000000, std::memory_order_release);
 
 #if defined(_DEBUG) || defined(DEBUGFAST)
-  const char* const type = mailbox == MAILBOX_DSP ? "DSP" : "CPU";
+  const char* const type = mailbox == Mailbox::DSP ? "DSP" : "CPU";
   DEBUG_LOG_FMT(DSP_MAIL, "{}(WM) B:{} M:{:#010x} (pc={:#06x})", type, mailbox,
                 PeekMailbox(mailbox), pc);
 #endif
@@ -82,10 +82,10 @@ void SDSP::WriteMailboxLow(Mailbox mailbox, u16 value)
 
 void SDSP::WriteMailboxHigh(Mailbox mailbox, u16 value)
 {
-  const u32 old_value = mbox[mailbox].load(std::memory_order_acquire);
+  const u32 old_value = GetMailbox(mailbox).load(std::memory_order_acquire);
   const u32 new_value = (old_value & 0xffff) | (value << 16);
 
-  mbox[mailbox].store(new_value & ~0x80000000, std::memory_order_release);
+  GetMailbox(mailbox).store(new_value & ~0x80000000, std::memory_order_release);
 }
 
 void SDSP::WriteIFX(u32 address, u16 value)
@@ -102,19 +102,19 @@ void SDSP::WriteIFX(u32 address, u16 value)
     break;
 
   case DSP_DMBH:
-    WriteMailboxHigh(MAILBOX_DSP, value);
+    WriteMailboxHigh(Mailbox::DSP, value);
     break;
 
   case DSP_DMBL:
-    WriteMailboxLow(MAILBOX_DSP, value);
+    WriteMailboxLow(Mailbox::DSP, value);
     break;
 
   case DSP_CMBH:
-    WriteMailboxHigh(MAILBOX_CPU, value);
+    WriteMailboxHigh(Mailbox::CPU, value);
     break;
 
   case DSP_CMBL:
-    WriteMailboxLow(MAILBOX_CPU, value);
+    WriteMailboxLow(Mailbox::CPU, value);
     break;
 
   case DSP_DSBL:
@@ -207,16 +207,16 @@ u16 SDSP::ReadIFXImpl(u16 address)
   switch (address & 0xff)
   {
   case DSP_DMBH:
-    return ReadMailboxHigh(MAILBOX_DSP);
+    return ReadMailboxHigh(Mailbox::DSP);
 
   case DSP_DMBL:
-    return ReadMailboxLow(MAILBOX_DSP);
+    return ReadMailboxLow(Mailbox::DSP);
 
   case DSP_CMBH:
-    return ReadMailboxHigh(MAILBOX_CPU);
+    return ReadMailboxHigh(Mailbox::CPU);
 
   case DSP_CMBL:
-    return ReadMailboxLow(MAILBOX_CPU);
+    return ReadMailboxLow(Mailbox::CPU);
 
   case DSP_DSCR:
     return ifx_regs[address & 0xFF];
diff --git a/Source/Core/Core/HW/DSPLLE/DSPLLE.cpp b/Source/Core/Core/HW/DSPLLE/DSPLLE.cpp
index 03a9cefc43..2dc420864d 100644
--- a/Source/Core/Core/HW/DSPLLE/DSPLLE.cpp
+++ b/Source/Core/Core/HW/DSPLLE/DSPLLE.cpp
@@ -213,25 +213,25 @@ u16 DSPLLE::DSP_ReadControlRegister()
 
 u16 DSPLLE::DSP_ReadMailBoxHigh(bool cpu_mailbox)
 {
-  return m_dsp_core.ReadMailboxHigh(cpu_mailbox ? MAILBOX_CPU : MAILBOX_DSP);
+  return m_dsp_core.ReadMailboxHigh(cpu_mailbox ? Mailbox::CPU : Mailbox::DSP);
 }
 
 u16 DSPLLE::DSP_ReadMailBoxLow(bool cpu_mailbox)
 {
-  return m_dsp_core.ReadMailboxLow(cpu_mailbox ? MAILBOX_CPU : MAILBOX_DSP);
+  return m_dsp_core.ReadMailboxLow(cpu_mailbox ? Mailbox::CPU : Mailbox::DSP);
 }
 
 void DSPLLE::DSP_WriteMailBoxHigh(bool cpu_mailbox, u16 value)
 {
   if (cpu_mailbox)
   {
-    if ((m_dsp_core.PeekMailbox(MAILBOX_CPU) & 0x80000000) != 0)
+    if ((m_dsp_core.PeekMailbox(Mailbox::CPU) & 0x80000000) != 0)
     {
       // the DSP didn't read the previous value
       WARN_LOG_FMT(DSPLLE, "Mailbox isn't empty ... strange");
     }
 
-    m_dsp_core.WriteMailboxHigh(MAILBOX_CPU, value);
+    m_dsp_core.WriteMailboxHigh(Mailbox::CPU, value);
   }
   else
   {
@@ -243,7 +243,7 @@ void DSPLLE::DSP_WriteMailBoxLow(bool cpu_mailbox, u16 value)
 {
   if (cpu_mailbox)
   {
-    m_dsp_core.WriteMailboxLow(MAILBOX_CPU, value);
+    m_dsp_core.WriteMailboxLow(Mailbox::CPU, value);
   }
   else
   {