Avatar of AbdulBasith Syed
AbdulBasith SyedFlag for Saudi Arabia

asked on 

Mail Rejected: SMTP Authentication

I had this question after viewing exchange external email repeatedly blocked/undelivered.

i have a similar issue. my exchange was working good fro past 3 years , but now from past few weeks we are getting rejection messages

Please turn on SMTP Authentication in your mail client. exch2013.kbrokerage.com []:35454 is not permitted to relay through this server without authentication.
A problem occurred while delivering this message to this email address. Try sending this message again. If the problem continues, please contact your helpdesk.

i am unable to find out the reason for this. I tried using a new send connector with smart host and basic authentication. before i was using send connector with MX
Exchange* SMTP

Avatar of undefined
Last Comment
AbdulBasith Syed
Avatar of Satish Auti
Satish Auti
Flag of India image

Is your smart host managed by your ISP?
Avatar of AbdulBasith Syed


We have been using the MX record and external DNS. We never used smart host, so basically its not the ISP. i have attached image for the setting we are using  on send connector for the past 3 years
Avatar of Jude Perera
Jude Perera
Flag of Sri Lanka image

Hi AbdulBasith Syed,

Can you try to send the email using OWA? If it gets delivered then it's a client side issue. If the client is using IMAP as connectivity type then ensure that the outgoing server is same as the incoming.

Avatar of AbdulBasith Syed


Hi Jude,
All are exchange clients RPC/HTTP, so there will be no option for outgoing server.  
i dont think IMAP is the issue in my scenario.
its sending through  exch2013.kbrokerage.com, if its IMAP the outgoing server will be imap.kbrokerage.com
Avatar of Satish Auti
Satish Auti
Flag of India image

Is this problem face by user or have you configure SMTP relay like functional mailbox something like that, for mailing purpose.
Is there any spam filter in you environment?

if possible please share full NDR report.
Avatar of AbdulBasith Syed
AbdulBasith Syed
Flag of Saudi Arabia image

Blurred text
View this solution by signing up for a free trial.
Members can start a 7-Day free trial and enjoy unlimited access to the platform.
See Pricing Options
Start Free Trial
Avatar of AbdulBasith Syed


i found the solution.

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Top Experts
Get a personalized solution from industry experts
Ask the experts
Read over 600 more reviews


IBM logoIntel logoMicrosoft logoUbisoft logoSAP logo
Qualcomm logoCitrix Systems logoWorkday logoErnst & Young logo
High performer badgeUsers love us badge
LinkedIn logoFacebook logoX logoInstagram logoTikTok logoYouTube logo