diff --git a/backend/src/federation/client/1_0/model/SendCoinsArgs.ts b/backend/src/federation/client/1_0/model/SendCoinsArgs.ts
index 73e166308..ae9a01f58 100644
--- a/backend/src/federation/client/1_0/model/SendCoinsArgs.ts
+++ b/backend/src/federation/client/1_0/model/SendCoinsArgs.ts
@@ -27,6 +27,6 @@ export class SendCoinsArgs {
   @Field(() => String)
   senderUserName: string
 
-  @Field(() => String)
-  senderAlias: string
+  @Field(() => String, { nullable: true })
+  senderAlias?: string | null
 }
diff --git a/backend/src/graphql/resolver/TransactionResolver.ts b/backend/src/graphql/resolver/TransactionResolver.ts
index 1dbff7896..8d35708a6 100644
--- a/backend/src/graphql/resolver/TransactionResolver.ts
+++ b/backend/src/graphql/resolver/TransactionResolver.ts
@@ -38,7 +38,7 @@ import { calculateBalance } from '@/util/validate'
 import { virtualLinkTransaction, virtualDecayTransaction } from '@/util/virtualTransactions'
 
 import { BalanceResolver } from './BalanceResolver'
-import { getCommunityName, isCommunityAuthenticated, isHomeCommunity } from './util/communities'
+import { getCommunity, getCommunityName, isHomeCommunity } from './util/communities'
 import { findUserByIdentifier } from './util/findUserByIdentifier'
 import { getLastTransaction } from './util/getLastTransaction'
 import { getTransactionList } from './util/getTransactionList'
@@ -445,13 +445,17 @@ export class TransactionResolver {
       if (!CONFIG.FEDERATION_XCOM_SENDCOINS_ENABLED) {
         throw new LogError('X-Community sendCoins disabled per configuration!')
       }
-      if (!(await isCommunityAuthenticated(recipientCommunityIdentifier))) {
+      const recipCom = await getCommunity(recipientCommunityIdentifier)
+      logger.debug('recipient commuity: ', recipCom)
+      if (recipCom === null) {
+        throw new LogError(
+          'no recipient commuity found for identifier:',
+          recipientCommunityIdentifier,
+        )
+      }
+      if (recipCom !== null && recipCom.authenticatedAt === null) {
         throw new LogError('recipient commuity is connected, but still not authenticated yet!')
       }
-      const recipCom = await DbCommunity.findOneOrFail({
-        where: { communityUuid: recipientCommunityIdentifier },
-      })
-      logger.debug('recipient commuity: ', recipCom)
       let pendingResult: SendCoinsResult
       let committingResult: SendCoinsResult
       const creationDate = new Date()
diff --git a/federation/src/graphql/api/1_0/model/SendCoinsArgs.ts b/federation/src/graphql/api/1_0/model/SendCoinsArgs.ts
index 1337bbc6c..e15f40ed3 100644
--- a/federation/src/graphql/api/1_0/model/SendCoinsArgs.ts
+++ b/federation/src/graphql/api/1_0/model/SendCoinsArgs.ts
@@ -27,6 +27,6 @@ export class SendCoinsArgs {
   @Field(() => String)
   senderUserName: string
 
-  @Field(() => String)
-  senderAlias: string
+  @Field(() => String, { nullable: true })
+  senderAlias?: string | null
 }
diff --git a/federation/src/graphql/api/1_0/resolver/SendCoinsResolver.ts b/federation/src/graphql/api/1_0/resolver/SendCoinsResolver.ts
index a05ab2c7d..98f8af422 100644
--- a/federation/src/graphql/api/1_0/resolver/SendCoinsResolver.ts
+++ b/federation/src/graphql/api/1_0/resolver/SendCoinsResolver.ts
@@ -35,11 +35,13 @@ export class SendCoinsResolver {
       args.senderCommunityUuid,
       args.senderUserUuid,
       args.senderUserName,
+      args.senderAlias,
     )
     const result = new SendCoinsResult()
     // first check if receiver community is correct
     const homeCom = await DbCommunity.findOneBy({
       communityUuid: args.recipientCommunityUuid,
+      foreign: false,
     })
     if (!homeCom) {
       throw new LogError(
@@ -50,7 +52,10 @@ export class SendCoinsResolver {
     let receiverUser
     try {
       // second check if receiver user exists in this community
-      receiverUser = await findUserByIdentifier(args.recipientUserIdentifier)
+      receiverUser = await findUserByIdentifier(
+        args.recipientUserIdentifier,
+        args.recipientCommunityUuid,
+      )
     } catch (err) {
       logger.error('Error in findUserByIdentifier:', err)
       throw new LogError(
diff --git a/federation/src/graphql/util/findUserByIdentifier.ts b/federation/src/graphql/util/findUserByIdentifier.ts
index 96c9eb458..6b7f1bccc 100644
--- a/federation/src/graphql/util/findUserByIdentifier.ts
+++ b/federation/src/graphql/util/findUserByIdentifier.ts
@@ -6,12 +6,18 @@ import { LogError } from '@/server/LogError'
 
 import { VALID_ALIAS_REGEX } from './validateAlias'
 
-export const findUserByIdentifier = async (identifier: string): Promise<DbUser> => {
+export const findUserByIdentifier = async (
+  identifier: string,
+  communityIdentifier?: string,
+): Promise<DbUser> => {
   let user: DbUser | null
   if (validate(identifier) && version(identifier) === 4) {
-    user = await DbUser.findOne({ where: { gradidoID: identifier }, relations: ['emailContact'] })
+    user = await DbUser.findOne({
+      where: { gradidoID: identifier, communityUuid: communityIdentifier },
+      relations: ['emailContact'],
+    })
     if (!user) {
-      throw new LogError('No user found to given identifier', identifier)
+      throw new LogError('No user found to given identifier(s)', identifier, communityIdentifier)
     }
   } else if (/^.{2,}@.{2,}\..{2,}$/.exec(identifier)) {
     const userContact = await DbUserContact.findOne({
@@ -27,12 +33,22 @@ export const findUserByIdentifier = async (identifier: string): Promise<DbUser>
     if (!userContact.user) {
       throw new LogError('No user to given contact', identifier)
     }
+    if (userContact.user.communityUuid !== communityIdentifier) {
+      throw new LogError(
+        'Found user to given contact, but belongs to other community',
+        identifier,
+        communityIdentifier,
+      )
+    }
     user = userContact.user
     user.emailContact = userContact
   } else if (VALID_ALIAS_REGEX.exec(identifier)) {
-    user = await DbUser.findOne({ where: { alias: identifier }, relations: ['emailContact'] })
+    user = await DbUser.findOne({
+      where: { alias: identifier, communityUuid: communityIdentifier },
+      relations: ['emailContact'],
+    })
     if (!user) {
-      throw new LogError('No user found to given identifier', identifier)
+      throw new LogError('No user found to given identifier(s)', identifier, communityIdentifier)
     }
   } else {
     throw new LogError('Unknown identifier type', identifier)