Office 365 Error with Authentication is required for relay

Question asked by GW - 1/4/2019 at 2:12 AM

Unanswered

Hello,

Currently I am experiencing an issue with office 365 where our SM server sends out emails to the recipient's office 365 and get a bounce back "Authentication is required for relay" when the recipient's mailbox set to forward all incoming emails to us.

Furthermore, other public email account like google and yahoo will not have this issue because only our mail server set to "Require SMTP Authentication ".

So, is there any other methods or alternative solution to resolve it besides whitelisting all of office 365 outbound IPs?

7 Replies

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Linda Pagillo Replied

1/4/2019 at 2:43 PM

Hi Gary. I believe I know what is happening here. Can you post the smtp log for one of these messages so I can have a look. If you are not comfortable with posting it here, please email it to me at the address in my signature. Thanks!

Linda Pagillo
Mail's Best Friend
Email: linda.pagillo@mailsbestfriend.com
Web: www.mailsbestfriend.com

Authorized SmarterTools Reseller

Authorized Message Sniffer Reseller

GW Replied

1/7/2019 at 7:50 PM

Hi Linda,

Sorry for the late reply. Below is the SMTP log:

[From User laptop to recipient]

[2019.01.04] 11:12:48 [ORIGIN IP][34472143] rsp: 220 mail.mydomain.com Fri, 04 Jan 2019 03:12:48 +0000 UTC
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] connected at 1/4/2019 11:12:48 AM
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] IP in whitelist
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] IP in authentication bypass
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] cmd: EHLO USERLAPTOP
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] rsp: 250-mail.mydomain.com Hello [ORIGIN IP]250-SIZE 31457280250-AUTH LOGIN CRAM-MD5250-8BITMIME250 OK
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] cmd: AUTH LOGIN
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] rsp: 334 VXNlcm5hbWU6
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] Authenticating as user@mydomain.com
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] rsp: 334 UGFzc3dvcmQ6
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] rsp: 235 Authentication successful
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] Authenticated as user@mydomain.com
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] cmd: MAIL FROM: <user@mydomain.com>
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] rsp: 250 OK <user@mydomain.com> Sender ok
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] cmd: RCPT TO: <recipient@domain.com>
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] rsp: 250 OK <recipient@domain.com> Recipient ok
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] cmd: DATA
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] Performing PTR host name lookup for ORIGIN IP
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] PTR host name for ORIGIN IP resolved as UnknownHost
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] rsp: 354 Start mail input; end with <CRLF>.<CRLF>
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] rsp: 250 OK
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] Received message size: 2796 bytes
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] Successfully wrote to the HDR file. (D:\Spool\SubSpool0\145631816.hdr)
[2019.01.04] 11:12:48 [ORIGIN IP][34472143] Data transfer succeeded, writing mail to 145631816.eml
[2019.01.04] 11:12:51 [ORIGIN IP][34472143] cmd: QUIT
[2019.01.04] 11:12:51 [ORIGIN IP][34472143] rsp: 221 Service closing transmission channel
[2019.01.04] 11:12:51 [ORIGIN IP][34472143] disconnected at 1/4/2019 11:12:51 AM

[Recipient forward back to user]

[2019.01.04] 11:13:03 [40.107.132.73][26992696] rsp: 220 mail.mydomain.com Fri, 04 Jan 2019 03:13:03 +0000 UTC
[2019.01.04] 11:13:03 [40.107.132.73][26992696] connected at 1/4/2019 11:13:03 AM
[2019.01.04] 11:13:03 [40.107.132.73][26992696] cmd: EHLO APC01-PU1-obe.outbound.protection.outlook.com
[2019.01.04] 11:13:03 [40.107.132.73][26992696] rsp: 250-mail.mydomain.com Hello [40.107.132.73]250-SIZE 31457280250-AUTH CRAM-MD5250-8BITMIME250 OK
[2019.01.04] 11:13:03 [40.107.132.73][26992696] cmd: MAIL FROM:<user@mydomain.com> SIZE=26186 AUTH=<>
[2019.01.04] 11:13:03 [40.107.132.73][26992696] rsp: 550 Authentication is required for relay
[2019.01.04] 11:13:03 [40.107.132.73][26992696] cmd: QUIT
[2019.01.04] 11:13:03 [40.107.132.73][26992696] rsp: 221 Service closing transmission channel
[2019.01.04] 11:13:03 [40.107.132.73][26992696] disconnected at 1/4/2019 11:13:03 AM

Thanks for the prompt reply and hope there's an alternative to this issue

Linda Pagillo Replied

1/8/2019 at 3:31 PM

Thanks Gary. Ok, so here is what I think is happening... mail.mydomain.com sends the message to recipient@domain.com. recipient@domain.com forwards the mail from Microsoft's server back to your server where mail.mydomain.com lives. So in reality, I think to SM it looks like mail.mydomain.com is sending mail to itself, but using Microsoft's servers to send instead of yours and that's why it thinks it's relaying. I know this sounds confusing so if you need clarification, feel free to give me a call tomorrow at the number in my signature and I will be happy to explain as best I can. There will be no fee or charge for you call. Thanks! :)

Linda Pagillo
Mail's Best Friend
Email: linda.pagillo@mailsbestfriend.com
Web: www.mailsbestfriend.com

Authorized SmarterTools Reseller

Authorized Message Sniffer Reseller

GW Replied

1/8/2019 at 7:41 PM

Hi Linda,

Thanks for explaining the issue.

I do understand the issue but is there any way to overcome it, in SM settings or DNS settings?

Linda Pagillo Replied

1/8/2019 at 9:40 PM

Please allow me a bit of time to chat with a few colleagues of mine about this. I will get back with you asap. Thanks for your patience.

Also, if I may ask... why do some of your O365 users forward the mail back to your server? Is it easier for them to retrieve it there for some reason?

Linda Pagillo
Mail's Best Friend
Email: linda.pagillo@mailsbestfriend.com
Web: www.mailsbestfriend.com

Authorized SmarterTools Reseller

Authorized Message Sniffer Reseller

GW Replied

1/8/2019 at 11:36 PM

Okay, that would be great.

It's actually our use's customer O365 that will forward back to our user(Another domain) that is supporting their customer through another company entity.

Linda Pagillo Replied

1/9/2019 at 8:32 AM

Understood! I will do my best to get back with you with a solution later today.

Linda Pagillo
Mail's Best Friend
Email: linda.pagillo@mailsbestfriend.com
Web: www.mailsbestfriend.com

Authorized SmarterTools Reseller

Authorized Message Sniffer Reseller

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