Chilkat v11.3.0 Release Notes

Pinned December 16, 2025

  The main features of this release focus on Chilkat’s Ai class, enabling interactive AI response streaming directly into embedded desktop application browsers. It supports Azure, custom base URLs for OpenAI-compatible providers, and local providers like Ollama. ✨ New Features Ai Real-Time Streaming AI Responses to Embedded Browsers in Desktop Apps — Stream AI responses […]

Chilkat v11.2.0 Release Notes

Pinned November 3, 2025

Previous Version: Chilkat v11.1.0 Release Notes The main addition in v11.2.0 is the Chilkat.Ai class, and the Chilkat.StringBuilder.MarkdownToHtml method. Ai: The Chilkat AI class provides a unified API for interacting with different AI providers: OpenAI, Google, Claude, xAI, Perplexity, and DeepSeek. It provides functionality for conversation management, multimodal inputs, and streaming mode. Markdown to HTML […]

Semantic Versioning Starting with Chilkat 10.0.0

Pinned September 26, 2024

Starting with the v10.0.0 release (end of September 2024), Chilkat moves to standard semantic versioning.   Prior to this release, for various technical reasons, Chilkat was stuck with versions 9.5.0.xx, where only xx changed. For this first leap to semantic versioning, where the major version changes to 10 (from 9), there are no backward incompatible changes.  […]

Office365 – 451 4.7.0 Temporary server error. Please try again later. PRX5

May 3, 2024 in Office365

A Chilkat user is getting this error response from smtp.office365.com. He successfully got his OAuth2 access token, but then when trying to send the email, the Office365 server responded with this error indicating a temporary problem: “451 4.7.0 Temporary server error. Please try again later. PRX5 …” This is not an error caused because of […]

Office365 SMTP AUTH XOAUTH2 Fails with “535 5.7.3 Authentication unsuccessful”

April 17, 2024 in Office365

If you successfully minted an OAuth2 access token for your Azure Entra Id App, but then it fails when attempting to use it in the SMTP protocol for sending email with the error: AUTH XOAUTH2 user=xxx auth=Bearer ********************** 535 5.7.3 Authentication unsuccessful [BN9PXXXA0336.namprd03.prod.outlook.com 2024-04-16T12:11:26.548Z 08DC9999186DF999] Check your Entra Id App Registration to make sure you […]

How to Troubleshoot Office365 IMAP AUTHENTICATE XOAUTH2 Failed

April 8, 2024 in IMAP

Question: We have an issue reading mail and we see the below error message in log Login: DllDate: Oct 27 2023 ChilkatVersion: 9.5.0.96 UnlockPrefix: *** UnlockStatus: 2 Architecture: Little Endian; 32-bit Language: *** VerboseLogging: 0 imapServer: outlook.office365.com loginX(2219ms): login: abc@example.com greeting: * OK The Microsoft Exchange IMAP4 service is ready. [***] authenticateXOAuth2(2219ms): xoauth2Imap(2219ms): ConnectionType: SSL/TLS […]

Office365 App Setup for SMTP, POP, IMAP OAuth2 Client Credentials

December 24, 2023 in OAuth2

This blog post walks you through the complete Azure App Registration process, including the subsequent Exchange Online PowerShell commands needed to achieve the OAuth2 client credentials flow for Office365 email sending and reading via the SMTP, IMAP, and POP3 protocols. I wish there was an “easy button”, but unfortunately it does not exist. Step 1. […]

office365.com SMTP, POP3, IMAP OAuth2 Tips, Hints, and Solutions

December 12, 2022 in OAuth2

This page will be updated as time progresses with what we’ve learned about getting things working with OAuth2 authentication for office365.com using the email protocols: SMTP, POP3, and IMAP. How do Other Office365 Users Send Email using my App Registered in my Azure Active Directory? It’s important to understand Tenancy in Azure Active Directory Apps.   […]

Office365 Modern Authentication for IMAP, POP3, and SMTP

August 13, 2022 in IMAP

This post documents how to implement Modern Authentication (OAuth2) for Office365 for the IMAP, POP3, and SMTP protocols.  The very first thing you’ll need to do is to create an “App Registration” in Azure Active Directory. See this Chilkat blog post for Instructions for Setting Up an App Registration in Azure for Modern Authentication for […]

Create Azure App Registration for use with IMAP, POP3, and SMTP

August 13, 2022 in Exchange Online

1) Go to https://portal.azure.com/#home and login to your Microsoft account. then go to Azure Active Directory.   2) Click On App Registrations * Copy your Tenant ID, you’ll need it later. 3) Click on “+ New registration” 4) Name your App and Click Register. Give it a name. For the Redirect URI, select “Web” and […]

smtp.office365.com – Failed to get initial SMTP Response

May 13, 2022 in Office365

If something on the client-side is blocking communications, such as a hardware or software firewall, or anti-virus, then it may be that a TLS connection is established, but then trying to read the 1st message from the server gets blocked.  When this happens, the contents of the LastErrorText look like this.   (The LastErrorText for a […]

SMTP / Office 365 / OAuth2 : SmtpCmdResp: 535 5.7.3 Authentication unsuccessful

May 11, 2022 in OAuth2

Question: A customer wants to send emails with Office 365 and OAuth2 Authentication. The setup of the application in Azure is OK. It works for one user. For another user we have the following error: SmtpCmdResp: 535 5.7.3 Authentication unsuccessful [****.****.prod.outlook.com] For authentication I use the example: https://www.example-code.com/powerbuilder/office365_oauth2_access_token.asp What is surprising is that for the […]

Office365 SMTP Error: 554 5.2.0 STOREDRV.Submission.Exception:SendAsDeniedException.MapiExceptionSendAsDenied;

June 9, 2020 in Office365

Question: I’m trying to send email using SMTP via smtp.office365.com, and I get this error: 554 5.2.0 STOREDRV.Submission.Exception:SendAsDeniedException.MapiExceptionSendAsDenied; Failed to process message due to a permanent exception with message Cannot submit message. 0.35250:0A001485, 1.36674:0A000000, 1.61250:00000000, 1.45378:02000000, 1.44866:59020000, 1.36674:0E000000, 1.61250:00000000, 1.45378:5E020000, 1.44866:F8000000, 16.55847:BC030000, 17.43559:0000000024020000000000000000000000000000, 20.52176:140FFA8B1500001000000000, 20.50032:140FFA8B8517001000000000, 0.35180:F1030000, 255.23226:09000000, 255.27962:0A000000, 255.27962:0E000000, 255.31418:F1030000, 0.35250:0300C981, 1.36674:0A000000, 1.61250:00000000, 1.45378:02000000, 1.44866:3A000000, […]