diff --git a/packages/backend/src/core/UserSuspendService.ts b/packages/backend/src/core/UserSuspendService.ts
index d594a223f4..cc8540f0ae 100644
--- a/packages/backend/src/core/UserSuspendService.ts
+++ b/packages/backend/src/core/UserSuspendService.ts
@@ -4,86 +4,127 @@
  */
 
 import { Inject, Injectable } from '@nestjs/common';
-import { Not, IsNull } from 'typeorm';
-import type { FollowingsRepository } from '@/models/_.js';
+import { Not, IsNull, Brackets, DataSource, EntityManager } from 'typeorm';
+import { bindThis } from '@/decorators.js';
+import { DI } from '@/di-symbols.js';
+import type Logger from '@/logger.js';
 import type { MiUser } from '@/models/User.js';
+import type { FollowingsRepository } from '@/models/_.js';
 import { QueueService } from '@/core/QueueService.js';
 import { GlobalEventService } from '@/core/GlobalEventService.js';
-import { DI } from '@/di-symbols.js';
 import { ApRendererService } from '@/core/activitypub/ApRendererService.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
-import { bindThis } from '@/decorators.js';
+import { LoggerService } from '@/core/LoggerService.js';
 
 @Injectable()
 export class UserSuspendService {
+	public logger: Logger;
+
 	constructor(
+		@Inject(DI.db)
+		private db: DataSource,
+
 		@Inject(DI.followingsRepository)
 		private followingsRepository: FollowingsRepository,
 
-		private userEntityService: UserEntityService,
 		private queueService: QueueService,
 		private globalEventService: GlobalEventService,
 		private apRendererService: ApRendererService,
+		private userEntityService: UserEntityService,
+		private loggerService: LoggerService,
 	) {
+		this.logger = this.loggerService.getLogger('account:suspend');
 	}
 
 	@bindThis
 	public async doPostSuspend(user: { id: MiUser['id']; host: MiUser['host'] }): Promise<void> {
+		this.logger.warn(`doPostSuspend: ${user.id} (host: ${user.host})`);
+
 		this.globalEventService.publishInternalEvent('userChangeSuspendedState', { id: user.id, isSuspended: true });
 
 		if (this.userEntityService.isLocalUser(user)) {
 			// 知り得る全SharedInboxにDelete配信
 			const content = this.apRendererService.addContext(this.apRendererService.renderDelete(this.userEntityService.genLocalUserUri(user.id), user));
 
-			const queue: string[] = [];
+			this.logger.info(`Delivering delete activity to all shared inboxes of ${user.id}`);
+			await this.db.transaction(async (transactionalEntityManager: EntityManager) => {
+				const inboxesCte = transactionalEntityManager.createQueryBuilder()
+					.select('distinct coalesce(following.followerSharedInbox, following.followeeSharedInbox)', 'inbox')
+					.from(this.followingsRepository.metadata.targetName, 'following')
+					.where(new Brackets((qb) => qb.where({ followerHost: Not(IsNull()) }).orWhere({ followeeHost: Not(IsNull()) })))
+					.andWhere(new Brackets((qb) => qb.where({ followerSharedInbox: Not(IsNull()) }).orWhere({ followeeSharedInbox: Not(IsNull()) })))
+					.orderBy('inbox');
 
-			const followings = await this.followingsRepository.find({
-				where: [
-					{ followerSharedInbox: Not(IsNull()) },
-					{ followeeSharedInbox: Not(IsNull()) },
-				],
-				select: ['followerSharedInbox', 'followeeSharedInbox'],
+				let offset = 0;
+				let cursor = '';
+				while (true) { // eslint-disable-line @typescript-eslint/no-unnecessary-condition, no-constant-condition
+					const inboxes = await transactionalEntityManager.createQueryBuilder().addCommonTableExpression(inboxesCte, 'inboxes')
+						.select('inbox').from('inboxes', 'inboxes').where('inbox > :cursor', { cursor }).limit(500).getRawMany<{ inbox: string }>()
+						.then((rows) => rows.map((row) => row.inbox));
+
+					if (inboxes.length === 0) break;
+
+					this.logger.info(`Delivering delete activity to ${offset} - ${offset + inboxes.length} shared inboxes of ${user.id}`);
+					for (const inbox of inboxes) {
+						try {
+							this.queueService.deliver(user, content, inbox, true);
+						} catch (err) {
+							this.logger.error(`Failed to deliver delete activity to ${inbox}: ${err}`, { error: err, inbox });
+						}
+					}
+
+					offset += inboxes.length;
+					cursor = inboxes[inboxes.length - 1];
+				}
 			});
 
-			const inboxes = followings.map(x => x.followerSharedInbox ?? x.followeeSharedInbox);
-
-			for (const inbox of inboxes) {
-				if (inbox != null && !queue.includes(inbox)) queue.push(inbox);
-			}
-
-			for (const inbox of queue) {
-				this.queueService.deliver(user, content, inbox, true);
-			}
+			this.logger.info(`Scheduled delete activity delivery to all shared inboxes of ${user.id}`);
 		}
 	}
 
 	@bindThis
 	public async doPostUnsuspend(user: MiUser): Promise<void> {
+		this.logger.warn(`doPostUnsuspend: ${user.id}`);
+
 		this.globalEventService.publishInternalEvent('userChangeSuspendedState', { id: user.id, isSuspended: false });
 
 		if (this.userEntityService.isLocalUser(user)) {
 			// 知り得る全SharedInboxにUndo Delete配信
 			const content = this.apRendererService.addContext(this.apRendererService.renderUndo(this.apRendererService.renderDelete(this.userEntityService.genLocalUserUri(user.id), user), user));
 
-			const queue: string[] = [];
+			this.logger.info(`Delivering undo delete activity to all shared inboxes of ${user.id}`);
+			await this.db.transaction(async (transactionalEntityManager: EntityManager) => {
+				const inboxesCte = transactionalEntityManager.createQueryBuilder()
+					.select('distinct coalesce(following.followerSharedInbox, following.followeeSharedInbox)', 'inbox')
+					.from(this.followingsRepository.metadata.targetName, 'following')
+					.where(new Brackets((qb) => qb.where({ followerHost: Not(IsNull()) }).orWhere({ followeeHost: Not(IsNull()) })))
+					.andWhere(new Brackets((qb) => qb.where({ followerSharedInbox: Not(IsNull()) }).orWhere({ followeeSharedInbox: Not(IsNull()) })))
+					.orderBy('inbox');
 
-			const followings = await this.followingsRepository.find({
-				where: [
-					{ followerSharedInbox: Not(IsNull()) },
-					{ followeeSharedInbox: Not(IsNull()) },
-				],
-				select: ['followerSharedInbox', 'followeeSharedInbox'],
+				let offset = 0;
+				let cursor = '';
+				while (true) { // eslint-disable-line @typescript-eslint/no-unnecessary-condition, no-constant-condition
+					const inboxes = await transactionalEntityManager.createQueryBuilder().addCommonTableExpression(inboxesCte, 'inboxes')
+						.select('inbox').from('inboxes', 'inboxes').where('inbox > :cursor', { cursor }).limit(500).getRawMany<{ inbox: string }>()
+						.then((rows) => rows.map((row) => row.inbox));
+
+					if (inboxes.length === 0) break;
+
+					this.logger.info(`Delivering undo delete activity to ${offset} - ${offset + inboxes.length} shared inboxes of ${user.id}`);
+					for (const inbox of inboxes) {
+						try {
+							this.queueService.deliver(user, content, inbox, true);
+						} catch (err) {
+							this.logger.error(`Failed to deliver undo delete activity to ${inbox}: ${err}`, { error: err, inbox });
+						}
+					}
+
+					offset += inboxes.length;
+					cursor = inboxes[inboxes.length - 1];
+				}
 			});
 
-			const inboxes = followings.map(x => x.followerSharedInbox ?? x.followeeSharedInbox);
-
-			for (const inbox of inboxes) {
-				if (inbox != null && !queue.includes(inbox)) queue.push(inbox);
-			}
-
-			for (const inbox of queue) {
-				this.queueService.deliver(user as any, content, inbox, true);
-			}
+			this.logger.info(`Scheduled undo delete activity delivery to all shared inboxes of ${user.id}`);
 		}
 	}
 }