250 2.1.5 RESOLVER.GRP.Expanded; distribution list expanded - Recipient address rejected (FAIL when sending out to distribution list)

Question

Hello,

Asking you guys for help as my last hope...

I work in an IT department where the e-mail environment is hybrid, a Exchange 2013 on-prem server and Microsoft 365.

All the users are are migrated to 365, but the original domain addresses, as economy@companyname.com, invoice@companyname.com, is still running on the exchange server.

Every monday night an email is been sent from the system to several users. The sendlist contains several distribution lists, about 4-5 DL. Every DL is about 10 users, so there is not a lot. But every monday morning I starts the week with an error message which comes in return from the fail. Its always the same two users. The two users is founded in different DL.

user@companyname.comAM2PEPF0001C70B.mail.protection.outlook.comRemote Server returned '<X.mail.protection.outlook.com #5.4.1 smtp;550 5.4.1 Recipient address rejected: Access denied. [X.eurxxx0.prod.outlook.com 2024-04-22T02:19:24.492Z X]>'

user2@companyname.comAM2PEPF0001C70B.mail.protection.outlook.comRemote Server returned '<X.mail.protection.outlook.com #5.4.1 smtp;550 5.4.1 Recipient address rejected: Access denied. [X.eurxxx0.prod.outlook.com 2024-04-22T02:19:25.164Z X]>'

When I run a messagetrace on the message on the certian user on the Exchange server I get:

Sender            : mail@companyname.comRecipients        : {All users, user1, user2,user3...}
RecipientStatus   : {250 2.1.5 RESOLVER.GRP.Expanded; distribution list expanded}
RecipientCount    : 9
Timestamp         : 4/22/2024 4:19:21 AM
EventId           : EXPAND
SourceContext     : Exchange-server-name
Source            : ROUTING
MessageSubject    : ...
MessageId         : ...
InternalMessageId : ...
RecipientStatus   : {250 2.1.5 RESOLVER.GRP.Expanded; distribution list expanded}
RecipientCount    : 9
ReturnPath        : sender email-adress

I just dont get why its always these two users. I´ve checked that they are members of the DL-group. I´ve tried removing them and adding them back, but still I receive these error. Any ideas?

Thanks in advance...!

Answer 1

I would look at the remote routing address of those two accounts.

Make sure

1. Its valid (user@<domain>.mail.onmicosoft.com
2. That 1 above is set as the remote routing address and that email address is synced to Exchange Online