HubSpot

HubSpot connects each person's Microsoft 365 inbox with Microsoft Graph, and sends their one-to-one email through it. Footer365 signs that mail, because it passes through your Microsoft 365. Choose how your CRM or app sends its mail explains the two ways to send, and this guide follows the first.

At a glance

• Can be signed: one-to-one email and sequences sent from a person's connected inbox. HubSpot says they "do not use HubSpot's email sending network" and are "sent over the network of the inbox you connected."
• Cannot be signed: marketing email and automated (workflow) email, which HubSpot says are "sent through HubSpot's own email sending network", and a HubSpot-hosted conversations inbox, where HubSpot says "all sends will go through HubSpot's email sending network."
• How it connects: "HubSpot uses the Microsoft Graph API to integrate with your inbox and calendar", and the connection "uses OAuth, a form of Modern Authentication."
• Status: from HubSpot's documentation as read on 23 October 2026, not tested by Footer365.

Before you start

• Footer365 mail flow is set up. With the Outlook add-in only, no mail HubSpot sends is signed. Using the Outlook add-in only
• Every person who sends from HubSpot has a Footer365 signature rule that covers them.
• HubSpot says connecting needs the "Personal email access" permission, and that a user with a View-Only seat "cannot connect their individual work emails to HubSpot."
• Your Microsoft 365 organisation may need an administrator to approve HubSpot, as in step 1.

Step 1: Approve the app in Microsoft 365

HubSpot asks for these Microsoft Graph scopes: Mail.ReadWrite, Mail.Send, Calendars.Read, Calendars.ReadWrite, offline_access, email, openid and User.Read. If a person sees "Need admin approval", HubSpot gives three ways round it:

1. Allow user consent for verified publishers. Turn on Allow user consent for apps from verified publishers, for selected permissions (Recommended). HubSpot says it is a verified publisher, so people can then connect their own inbox.
2. Let people ask. Turn on Users can request admin consent to apps they are unable to consent to. Administrators then see the requests on the Admin consent requests page.
3. Approve for the whole organisation. Use HubSpot's admin consent address, with your tenant ID. HubSpot says that after consenting, the administrator must add the users to the "HubSpot Sales" app under Enterprise applications, and that an error shown after consent can be ignored.

The three settings are in your Microsoft Entra admin centre, and Approve an app's access in Microsoft 365 explains where and who can change each. HubSpot's own page gives the consent address: Troubleshoot Office 365 inbox and calendar connection errors.

Step 2: Choose the mailbox

• Each person's own mailbox is what HubSpot's connected inbox is for. The mail is signed with the signature your rules give that person.
• A shared mailbox: HubSpot says "Microsoft 365 shared mailboxes" are not supported when connecting an individual work email, so a person cannot connect sales@ or support@ that way. HubSpot's team email, below, is separate.

Step 3: Connect it in HubSpot

Each person does this, following HubSpot's steps:

1. Select the settings icon in the top navigation bar, then General in the left sidebar, then the Email tab.
2. Select Connect email account, then Connect your inbox.
3. Enter your email address and select Next, then connect to your provider. If HubSpot does not identify it, select I want to choose my email provider myself and choose Microsoft Outlook.
4. Select Continue, sign in with your Microsoft 365 account, and select Allow if asked.

HubSpot's own steps: Connect your inbox to HubSpot.

Step 4: Check one message

1. Send a one-to-one email from HubSpot to an address outside your organisation that you can read.
2. Open the headers of the copy you receive.
3. Return-Path should be the sender's own address, and X-Footer365-Relay-Id should be there.
4. Look in the sender's Sent Items. HubSpot's pages do not say whether the message is saved there, so its absence is not a fault by itself.

What other results mean: Mail from our CRM is not signed.

Where the signature goes

The HubSpot pages read do not describe a personal signature setting for the connected inbox, so this guide says nothing about it. If people have set one in HubSpot, the message may carry two signatures. Check one message, and leave HubSpot's empty if you see two. To put Footer365's signature where a HubSpot template ends, use a marker, and check one message, because HubSpot's pages do not say what it does with text in double braces. Place the signature with a marker

What is not signed

• Marketing email and workflow email. HubSpot says: "When you send an email using the marketing email tool or an automated email using the workflows tool" it is "sent through HubSpot's own email sending network."
• A HubSpot-hosted conversations inbox. HubSpot says: "Once configured, all sends will go through HubSpot's email sending network." Its page for connecting a team email lets you choose Office 365, but does not say whether replies then go through the mailbox, so check one reply.
• Transactional email sent by HubSpot's network.

HubSpot's explanation of which email goes where: Understand email sending in HubSpot.

What stops working

HubSpot's page says its connection uses Microsoft Graph, so it does not depend on Exchange Web Services or on a stored password. HubSpot lists these Microsoft-side faults that stop a connected inbox:

• An application access policy that restricts HubSpot ("Access to OData is disabled"), which an IT administrator must update so HubSpot is not restricted.
• A mailbox "not enabled for REST API access", which needs a mailbox hosted in Exchange Online with an active licence.
• An inbox that shows as outlook_ followed by characters at outlook.com, which HubSpot says "can cause issues with sending or syncing your emails from your connected inbox".

Limits

HubSpot's pages read state no daily sending limit for the connected inbox. Microsoft's limits for a mailbox apply: 10,000 recipients a day and 30 messages a minute. Microsoft: Exchange Online limits

Last resort: a connector to Exchange Online

HubSpot's pages read describe no connector from HubSpot into Exchange Online, and HubSpot runs on its own servers. Microsoft says a connector cannot be used for a service hosted by someone else, and asks such a service for a certificate of your own. So there is no connector route for HubSpot mail. Mail HubSpot sends from its own network cannot be signed. Last resort: a connector to Exchange Online

If it does not work

1. A person cannot connect, and sees "Need admin approval". Approve an app's access in Microsoft 365
2. The connection keeps dropping. Check the Microsoft-side faults above.
3. The message has no X-Footer365-Relay-Id. It did not pass through Microsoft 365. It may be marketing, workflow or hosted-inbox email.
4. It passed through Footer365 but is unsigned. The signature was not added
5. Still not clear. Mail from our CRM is not signed

Campaign clicks in HubSpot

Separately from signing the email HubSpot sends, Footer365 can write each human click on a campaign banner to HubSpot, as a note on the company the message went to, matched by the recipient's organisation domain and never their address. A Super Admin connects it on Developers > Integrations. See Send campaign clicks to HubSpot.

Sources

Read on 23 October 2026:

• HubSpot: Connect your inbox to HubSpot, last updated 28 September 2026.
• HubSpot: Troubleshoot Office 365 inbox and calendar connection errors, last updated 15 October 2026.
• HubSpot: Understand email sending in HubSpot, last updated 14 October 2026.
• HubSpot: Connect channels to the conversations inbox, last updated 9 September 2026.