Send e-mail from Office 365 Accounts with username/password authentication (non-interactive mode)

This tutorial demonstrates how to send e-mail via SMTP with Office 365 in the classic username/password way (not using OAuth 2.0).

At the moment of writing (Jan-2026) Microsoft 365 / Office 365 still allows the apps to send e-mails via SMTP and username/password authentication.

This, however, requires disabling two-factor auth (because in this case the email is being sent by a program in non-interactive scenario, not by a human who can respond to 2FA request).

Make sure that security defaults for O365 tenant are disabled (this disables 2FA requirement).

// Add to the top of your code file (if not already present)
using MailBee;
using MailBee.SmtpMail;

...

MailBee.Global.LicenseKey = "License key";

Smtp mailer = new Smtp();

mailer.Log.Enabled = true;
mailer.Log.Filename = @"C:\Temp\log.txt";
mailer.Log.Clear();

mailer.SmtpServers.Add("smtp.office365.com", "myemail@mytenant.onmicrosoft.com", "password").Port = 587;

mailer.From.AsString = "myemail@mytenant.onmicrosoft.com";
mailer.To.AsString = "support@afterlogic.com";
mailer.Subject = "Test";
mailer.Send();

' Add to the top of your code file (if not already present)
Imports MailBee
Imports MailBee.SmtpMail

...

MailBee.Global.LicenseKey = "License key"

Dim mailer As New Smtp()

mailer.Log.Enabled = True
mailer.Log.Filename = "C:\Temp\log.txt"
mailer.Log.Clear()

mailer.SmtpServers.Add("smtp.office365.com", "myemail@mytenant.onmicrosoft.com", "password").Port = 587

mailer.From.AsString = "myemail@mytenant.onmicrosoft.com"
mailer.To.AsString = "support@afterlogic.com"
mailer.Subject = "Test"
mailer.Send()