{"id":4356,"date":"2026-10-13T15:30:39","date_gmt":"2026-10-13T13:30:39","guid":{"rendered":"https:\/\/vivatec.de\/?post_type=product&#038;p=4356"},"modified":"2026-10-15T15:49:54","modified_gmt":"2026-10-15T13:49:54","slug":"vivatec-smtp-relay","status":"publish","type":"product","link":"https:\/\/vivatec.de\/en\/product\/vivatec-smtp-relay\/","title":{"rendered":"VivaTec SMTP Relay"},"content":{"rendered":"<h2>Secure email delivery from existing systems through Microsoft 365<\/h2>\n<p>Many applications, server services and on-premises mail servers can send email reliably via SMTP but do not support modern OAuth2 authentication with Microsoft 365.<\/p>\n<p>VivaTec SMTP Relay bridges this gap.<\/p>\n<p>The application accepts email from your local network via SMTP and securely forwards it through Microsoft 365 \/ Exchange Online. It authenticates using OAuth2 \/ XOAUTH2 and a certificate rather than a permanently stored user password.<\/p>\n<p>This lets you continue using existing systems without requiring them to support OAuth2.<\/p>\n<h2>Ideal for on-premises Microsoft Exchange servers<\/h2>\n<p>An on-premises Microsoft Exchange server can also use VivaTec SMTP Relay as a smart host.<\/p>\n<p>Exchange Server supports modern authentication in various client and hybrid scenarios. However, a traditional Send Connector using a smart host does not provide OAuth2 \/ XOAUTH2 authentication to that smart host.<\/p>\n<p>VivaTec SMTP Relay handles modern authentication on its behalf and securely forwards messages through Exchange Online.<\/p>\n<p>Typical mail flow:<\/p>\n<p>On-premises Microsoft Exchange server<br \/>\u2192 SMTP \/ SmartHost<br \/>\u2192 VivaTec SMTP Relay<br \/>\u2192 STARTTLS + OAuth2 \/ XOAUTH2<br \/>\u2192 Microsoft 365 \/ Exchange Online<\/p>\n<h2>Typical use cases<\/h2>\n<ul>\n<li>on-premises Microsoft Exchange servers using smart host delivery<\/li>\n<li>HCL Domino and HCL Verse<\/li>\n<li>inventory management and ERP systems<\/li>\n<li>document management and archiving systems<\/li>\n<li>multifunction printers and scanners<\/li>\n<li>legacy server applications<\/li>\n<li>custom business applications<\/li>\n<li>devices and services that only support traditional SMTP<\/li>\n<\/ul>\n<h2>Modern Microsoft 365 authentication<\/h2>\n<p>The sending system does not need to support OAuth2 or Microsoft Entra authentication itself.<\/p>\n<p>VivaTec SMTP Relay handles modern authentication with Microsoft 365 using STARTTLS and XOAUTH2.<\/p>\n<h2>Certificate-based authentication instead of a user password<\/h2>\n<p>VivaTec SMTP Relay connects to Microsoft 365 using a Microsoft Entra application and a locally stored certificate.<\/p>\n<p>Ongoing SMTP delivery therefore does not require a permanently stored user password.<\/p>\n<p>The private key remains in the server\u2019s Windows certificate store and does not need to be stored in a configuration file.<\/p>\n<h2>Targeted Exchange permissions<\/h2>\n<p>Exchange Online Application RBAC lets you specify which mailboxes the relay is permitted to send messages from.<\/p>\n<p>This restricts the application to the sender mailboxes it actually needs.<\/p>\n<h2>No open SMTP relay<\/h2>\n<p>Access to the local SMTP service can be restricted as required.<\/p>\n<p>You can define restrictions including:<\/p>\n<ul>\n<li>permitted source IP addresses<\/li>\n<li>permitted senders<\/li>\n<li>permitted sender domains<\/li>\n<li>mappings between local senders and Microsoft 365 mailboxes<\/li>\n<\/ul>\n<p>VivaTec SMTP Relay can therefore serve multiple internal systems centrally without operating as an open relay.<\/p>\n<h2>Local mail queue for reliable delivery<\/h2>\n<p>Incoming messages are stored locally before they are forwarded.<\/p>\n<p>If Microsoft 365 is temporarily unavailable, messages are retained and delivery is retried automatically.<\/p>\n<p>Supported features include:<\/p>\n<ul>\n<li>persistent local queue<\/li>\n<li>automatic retries<\/li>\n<li>error logging<\/li>\n<li>resuming delivery after a server or service restart<\/li>\n<\/ul>\n<h2>Guided Microsoft 365 setup<\/h2>\n<p>Setting up Microsoft Entra and Exchange Online normally requires several administrative steps.<\/p>\n<p>The built-in VivaTec SMTP Relay setup wizard helps with:<\/p>\n<ul>\n<li>Microsoft 365 administrator sign-in<\/li>\n<li>Microsoft 365 tenant detection<\/li>\n<li>creating or selecting the Entra application<\/li>\n<li>creating and assigning a certificate<\/li>\n<li>Exchange service principal<\/li>\n<li>Exchange RBAC permissions<\/li>\n<li>managing permitted sender mailboxes<\/li>\n<li>OAuth2 test<\/li>\n<li>XOAUTH2 SMTP test<\/li>\n<li>applying the required settings to the relay configuration<\/li>\n<\/ul>\n<h2>Runs as a Windows service<\/h2>\n<p>VivaTec SMTP Relay is designed for continuous operation in Windows Server environments.<\/p>\n<p>The relay runs in the background as a Windows service. A separate graphical configuration application lets you manage settings, the Microsoft 365 connection and diagnostics.<\/p>\n<h2>Benefits at a glance<\/h2>\n<ul>\n<li>continue using your existing SMTP systems<\/li>\n<li>suitable for on-premises Microsoft Exchange servers<\/li>\n<li>OAuth2 \/ XOAUTH2 connection to Microsoft 365<\/li>\n<li>no permanently stored SMTP user password required<\/li>\n<li>certificate-based authentication<\/li>\n<li>fine-grained Exchange permissions<\/li>\n<li>persistent local mail queue<\/li>\n<li>automatic retries<\/li>\n<li>IP address and sender restrictions<\/li>\n<li>guided Microsoft 365 setup<\/li>\n<li>Runs as a Windows service<\/li>\n<li>centralised configuration and diagnostics<\/li>\n<\/ul>\n<p>VivaTec SMTP Relay connects existing SMTP infrastructure to modern Microsoft 365 authentication without requiring the sending applications or mail servers to support OAuth2 themselves.<\/p>\n<p>For help with setup and operation, please get in touch via our <a href=\"https:\/\/vivatec.de\/en\/kontakt\/\">Contact<\/a>.<\/p>","protected":false},"excerpt":{"rendered":"<p>SMTP relay with OAuth2 support for Microsoft 365. Perpetual licence for one server installation.<\/p>","protected":false},"featured_media":4368,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"product_brand":[],"product_cat":[18],"product_tag":[46,38,50,42,47,48,37,43,39,45,36,41,44,40,49],"class_list":["post-4356","product","type-product","status-publish","has-post-thumbnail","product_cat-unkategorisiert","product_tag-basic-authentication-alternative","product_tag-exchange-online","product_tag-exchange-send-connector","product_tag-exchange-server-smarthost","product_tag-hcl-domino-smtp","product_tag-legacy-smtp","product_tag-microsoft-365-smtp-relay","product_tag-microsoft-entra-id","product_tag-oauth2-smtp","product_tag-smtp-gateway","product_tag-smtp-relay","product_tag-smtp-smarthost","product_tag-windows-smtp-relay","product_tag-xoauth2","product_tag-zertifikatsauthentifizierung","first","instock","virtual","sold-individually","taxable","purchasable","product-type-simple"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>VivaTec SMTP Relay \u2013 OAuth2 SMTP Relay f\u00fcr Microsoft 365<\/title>\n<meta name=\"description\" content=\"VivaTec SMTP Relay verbindet lokale Exchange Server, HCL Domino, ERP-Systeme und \u00e4ltere SMTP-Anwendungen sicher per OAuth2\/XOAUTH2 mit Microsoft 365.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/vivatec.de\/en\/product\/vivatec-smtp-relay\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"VivaTec SMTP Relay \u2013 OAuth2 SMTP Relay f\u00fcr Microsoft 365\" \/>\n<meta property=\"og:description\" content=\"VivaTec SMTP Relay verbindet lokale Exchange Server, HCL Domino, ERP-Systeme und \u00e4ltere SMTP-Anwendungen sicher per OAuth2\/XOAUTH2 mit Microsoft 365.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/vivatec.de\/en\/product\/vivatec-smtp-relay\/\" \/>\n<meta property=\"og:site_name\" content=\"VivaTec - makes it work\" \/>\n<meta property=\"article:modified_time\" content=\"2026-10-15T13:49:54+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/vivatec.de\/wp-content\/uploads\/2026\/10\/relay-logo.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1254\" \/>\n\t<meta property=\"og:image:height\" content=\"1254\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"4 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/vivatec.de\\\/produkt\\\/vivatec-smtp-relay\\\/\",\"url\":\"https:\\\/\\\/vivatec.de\\\/produkt\\\/vivatec-smtp-relay\\\/\",\"name\":\"VivaTec SMTP Relay \u2013 OAuth2 SMTP Relay f\u00fcr Microsoft 365\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/vivatec.de\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/vivatec.de\\\/produkt\\\/vivatec-smtp-relay\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/vivatec.de\\\/produkt\\\/vivatec-smtp-relay\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/vivatec.de\\\/wp-content\\\/uploads\\\/2026\\\/10\\\/relay-logo.png\",\"datePublished\":\"2026-10-13T13:30:39+00:00\",\"dateModified\":\"2026-10-15T13:49:54+00:00\",\"description\":\"VivaTec SMTP Relay verbindet lokale Exchange Server, HCL Domino, ERP-Systeme und \u00e4ltere SMTP-Anwendungen sicher per OAuth2\\\/XOAUTH2 mit Microsoft 365.\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/vivatec.de\\\/produkt\\\/vivatec-smtp-relay\\\/#breadcrumb\"},\"inLanguage\":\"en-GB\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/vivatec.de\\\/produkt\\\/vivatec-smtp-relay\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-GB\",\"@id\":\"https:\\\/\\\/vivatec.de\\\/produkt\\\/vivatec-smtp-relay\\\/#primaryimage\",\"url\":\"https:\\\/\\\/vivatec.de\\\/wp-content\\\/uploads\\\/2026\\\/10\\\/relay-logo.png\",\"contentUrl\":\"https:\\\/\\\/vivatec.de\\\/wp-content\\\/uploads\\\/2026\\\/10\\\/relay-logo.png\",\"width\":1254,\"height\":1254,\"caption\":\"VivaTec SMTP Relay f\u00fcr Microsoft 365 OAuth2 und Exchange Online\"},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/vivatec.de\\\/produkt\\\/vivatec-smtp-relay\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Start\",\"item\":\"https:\\\/\\\/vivatec.de\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"VivaTec SMTP Relay\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/vivatec.de\\\/#website\",\"url\":\"https:\\\/\\\/vivatec.de\\\/\",\"name\":\"VivaTec - makes it work\",\"description\":\"Software, Hardware, NET &amp; 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