Forum Discussion
Can't send SMTP mail after setting Default Security in Office 365
LusoAdmin Hey there. I'll put the solution here because as far as I can tell, everyone should also have that problem now. It took 1 week with the Microsoft support to finally find the solution. Just like I thought, because now the default security is enabled when you create a new tenant, even if you disable it, smtp somehow stays disabled and that overrides the settings in your admin panel.
All you have to do is enable it in Powershell. To connect with Powershell, first you have to execute this:
Connect-MsolService
Import-Module ExchangeOnlineManagement
Connect-ExchangeOnlineThen you enter your admin credentials. After that, you can check the "smtp disabled" flag, it should be set to "true":
Get-TransportConfig | Format-List SmtpClientAuthenticationDisabled
To enable smtp and get things working again, you enter this command:
Set-TransportConfig -SmtpClientAuthenticationDisabled $false
Worked for all my tenants. I hope this helps you too!
I just enabled Security Defaults in our Office 365 tenant as well the other day and also have the same problem (from an app that uses SMTP). I disabled Security Defaults but the app still can't send through SMTP anymore. Even tried disabling MFA = still not working.
Did you get a resolution to your issue in the end?
I know this is an old thread, but I'm having the same problem as @BinhTang . For half my tenants smtp does not work even with Default Security disabled. I found there is some kind of Azure security that disable Legacy SMTP and that ovverides the settings in the Admin panel. So I think once the tenants are created with the default Security settings or if you enable it, you're screwed since you can't go back and change those settings in Azure if you don't have it. I opened a ticket with Microsoft and so far they have not been able to solve my problem.
- Today I had the problem again with a new Office 365 tenant. He couldn't send smtp mails. It looks like MS is activating the Default Security for new tenant now. Lukely, after disabling the Default Security smtp sending was working.
