diff --git a/api/src/gateway/gateway.dto.ts b/api/src/gateway/gateway.dto.ts
index 63df517..9659e63 100644
--- a/api/src/gateway/gateway.dto.ts
+++ b/api/src/gateway/gateway.dto.ts
@@ -468,6 +468,13 @@ export class HeartbeatInputDTO {
   })
   receiveSMSEnabled?: boolean
 
+  @ApiProperty({
+    type: Number,
+    required: false,
+    description: 'SMS send delay in seconds (0-3600), used by device queue',
+  })
+  smsSendDelaySeconds?: number
+
   @ApiProperty({ type: SimInfoCollectionDTO, required: false })
   simInfo?: SimInfoCollectionDTO
 }
diff --git a/api/src/gateway/gateway.service.ts b/api/src/gateway/gateway.service.ts
index 32467ec..98c3fa7 100644
--- a/api/src/gateway/gateway.service.ts
+++ b/api/src/gateway/gateway.service.ts
@@ -1089,6 +1089,15 @@ const updatedSms = await this.smsModel.findByIdAndUpdate(
       updateData.receiveSMSEnabled = input.receiveSMSEnabled
     }
 
+    // Update smsSendDelaySeconds if provided (clamp 0-3600)
+    if (input.smsSendDelaySeconds !== undefined) {
+      const clamped = Math.min(
+        3600,
+        Math.max(0, Math.floor(Number(input.smsSendDelaySeconds))),
+      )
+      updateData.smsSendDelaySeconds = clamped
+    }
+
     // Update batteryInfo if provided
     if (input.batteryPercentage !== undefined || input.isCharging !== undefined) {
       if (input.batteryPercentage !== undefined) {
diff --git a/api/src/gateway/schemas/device.schema.ts b/api/src/gateway/schemas/device.schema.ts
index 7bdb2d2..d6657e6 100644
--- a/api/src/gateway/schemas/device.schema.ts
+++ b/api/src/gateway/schemas/device.schema.ts
@@ -4,6 +4,9 @@ import { User } from '../../users/schemas/user.schema'
 
 export type DeviceDocument = Device & Document
 
+/** Default delay between SMS sends (seconds). 5s helps avoid carrier/device throttling. */
+export const DEFAULT_SMS_SEND_DELAY_SECONDS = 5
+
 @Schema({ timestamps: true })
 export class Device {
   _id?: Types.ObjectId
@@ -62,6 +65,9 @@ export class Device {
   @Prop({ type: Boolean, default: false })
   receiveSMSEnabled: boolean
 
+  @Prop({ type: Number, default: DEFAULT_SMS_SEND_DELAY_SECONDS })
+  smsSendDelaySeconds: number
+
   @Prop({ type: Date })
   lastHeartbeat: Date