DEV Community: Katrina Aquino

Mailbox unavailable. The server response was: 5.7.1 Service unavailable, Client host [IP ADDRESS] blocked using Spamhaus.

Katrina Aquino — Fri, 12 Jul 2024 01:22:34 +0000

Mailbox unavailable. The server response was: 5.7.1 Service unavailable, Client host [IP ADDRESS] blocked using Spamhaus. To request removal from this list see https://www.spamhaus.org/query/ip/IP ADDRESS AS(1450)

The SMTP server requires a secure connection. The server response was: 5.7.57 Client not authenticated to send mail.

Katrina Aquino — Thu, 04 Jul 2024 08:28:50 +0000

Are you experincing this error code while trying to configure your custom application to integrate using Microsoft 365:

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.57 Client not authenticated to send mail. Error: 535 5.7.139 Authentication unsuccessful, user is locked by your organization's security defaults policy. Contact your administrator.

This error means you used right settings but not suitable to the custom application and 365.

If you are not familiar what are the smtp settings you can used for 3rd part and custom application to be able used 365 as email relay, Here's the reference:
_
https://learn.microsoft.com/en-us/exchange/mail-flow-best-practices/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-microsoft-365-or-office-365_

Of course, As the developer, email consultant or System admin. you gonna try and try different settings.

To be able to solve these solutions, we need to use app password for the custom application to bypass MFA Authentication (If your custom application can't do MFA/2-factor authentication)

*Here's the procedure to be able produce *

Enforce the MFA in admin center.
Open the office of the user > Initial logo > view account > security Info > Add sign-in method > app password > follow the instruction of MS until the app password shows

Kindly take note you need to copy and store carefully the password. basically, this is will be your password for your custom application.

We can now proceed for the SMTP settings in custom application:

_
_**
`Host = "domain.mail.protection.outlook.com",
Port = 25, //Recommended port is 587
EnableSsl = true,
DeliveryMethod = SmtpDeliveryMethod.Network,
UseDefaultCredentials = false,
TargetName = "STARTTLS/smtp.office365.com",
Credentials = new NetworkCredential(fromAddress.Address, fromPassword),

using (var client = new SmtpClient("Domain.mail.protection.outlook.com"))
{
client.UseDefaultCredentials = false;
client.Port = 587;
client.Credentials = new NetworkCredential("customapplication@domain.com", "app password we generated above");
client.EnableSsl = true;
`**_
_

Then you can now test.

Allow specific data file in Office365 for external recipients (Status code: 550 5.0.350)

Katrina Aquino — Fri, 05 Apr 2024 05:35:54 +0000

Are you admin and someone of the organization need to send a specific data file the must be attached in email rathen uploading it to onedrive and keep receiving this even you deploy this command in powershell?
_
$policy = Get-OwaMailboxPolicy [policy name]
$allowedFileTypes = $policy.AllowedFileTypes
$allowedFileTypes.Add(".foo")
Set-OwaMailboxPolicy $policy -AllowedFileTypes $allowedFileTypes*_*

or this

Set-OwaMailboxPolicy -Identity "" -AllowedFileTypes @{Add=".foo"}

Reference: https://techcommunity.microsoft.com/t5/exchange-team-blog/changes-to-file-types-blocked-in-outlook-on-the-web/ba-p/874451

Due of MS keeps blocking data file to secure the the tenants Worldwide. If your organization requires to receive and send specific file types that attached from Outlook then how we allow data files to not stop our users productivity and still keep our organization.

Solution:

Part 1: Change and add file type in Office365

Go to security portal or https://security.microsoft.com/ to our browser.

Look to your right panel, search for Email & collaboration and tap the arrow down to show the underling setting.

Under of email & collaboration, tap the policies and rules > threat policies > Anti-Malware > click the default policy

Default policy UI will be prompt, scroll-down and tap the edit protection settings

Once we clicked, the edit protection settings will be prompt. make sure the enable the common attachments filter is enable and under of this just tap the select file types.

Under of the select file types, Microsoft have default file types and add the specific file type such as .dat and done

You go back to edit protection settings, look for the when these file types are found then select the Quarantine the message and save.

Part 2: try to send email with the specific file type attached in email.

Take note: You must not receive any NDR in outlook.

Part 3: Where's the email
Now emails won't block, check to the Quarantine dashboard.

Security admin center (https://security.microsoft.com/) > Email & collaboration > Review > Quarantine > Approve the email.