Use SideQuest if your team runs Microsoft 365 or Outlook.

Step 1 Create a dedicated Gmail for SideQuest

Don't reuse a personal Gmail. Create a fresh one specifically for SideQuest so the label rules and forwarding don't tangle with your personal mail.

1. Go to accounts.google.com/signup and create a free Gmail. Pick a name like [email protected] — it's an internal address, no customer will ever see it.
2. Sign in to the new Gmail. Click the gear icon, then See all settings.
3. Under the Labels tab, click Create new label. Name it purchase-orders (exactly that, lowercase, with a hyphen). Save.

Step 2 Turn on forwarding in Microsoft 365 / Outlook

Microsoft 365 ("classic Outlook on the web") and Outlook.com use the same forwarding UI.

1. Sign in to outlook.office.com (for Microsoft 365) or outlook.live.com (for personal Outlook.com).
2. Click the gear icon (top right) → View all Outlook settings → Mail → Forwarding.
3. Tick Enable forwarding.
4. Paste the dedicated Gmail address from Step 1 into the Forward my email to field.
5. Tick Keep a copy of forwarded messages. (You want a record on Outlook's side too.)
6. Click Save.

If you're on the legacy Exchange Admin Center instead, the path is Recipients → Mailboxes → pick the mailbox → Manage email forwarding → Forward all messages.

Step 3 Add a Gmail filter to apply the purchase-orders label

Without a filter, forwarded mail lands in Gmail's inbox unlabeled and SideQuest never sees it.

1. Open the dedicated Gmail. Click the gear icon → See all settings → Filters and Blocked Addresses.
2. Click Create a new filter.
3. In the To field, enter your dedicated Gmail address (e.g., [email protected]).
4. Click Create filter.
5. Tick Apply the label and pick purchase-orders.
6. (Optional) Also tick Skip the Inbox if you don't want forwarded POs cluttering the Gmail inbox view.
7. Click Create filter.

If only some incoming mail is real POs (some is internal noise, support emails, etc.), narrow the filter using From (your buyer domains) or Has the words (e.g., "purchase order"). Tightening the filter is far easier than fixing a mis-labeled PO after the fact.

Step 4 Set up "Send mail as" so replies come from your real domain

This is the step that makes the buyer's reply look professional. SideQuest drafts the reply in Gmail; this setting controls what email address that reply appears to come from.

1. In the dedicated Gmail, click gear → See all settings → Accounts and Import.
2. Next to Send mail as, click Add another email address.
3. In the popup, enter your real customer-facing name (e.g., "Acme Distribution — Orders") and the real address (e.g., [email protected]). Untick Treat as an alias. Click Next Step.
4. Enter the SMTP server settings:
   • SMTP Server: smtp.office365.com
   • Port: 587
   • Username: your full Microsoft 365 mailbox address (e.g., [email protected])
   • Password: the mailbox password. If your account has multi-factor auth on, generate an app password in Microsoft 365 instead of using your real password.
   • Secured connection: TLS
5. Click Add Account. Gmail sends a verification code to that address. Open Outlook, grab the code, paste it back into Gmail's prompt.
6. Back on the Accounts and Import page, find the When replying to a message setting and pick Reply from the same address the message was sent to.

Step 5 Connect SideQuest to the dedicated Gmail

Same flow as any other SideQuest install — just point it at the dedicated Gmail instead of a personal one.

1. Run the SideQuest install. Install prompt walks you through it.
2. When the Gmail OAuth step asks you to sign in, sign in with the dedicated Gmail you created in Step 1.
3. The GMAIL_PO_LABEL in your .env should already be purchase-orders. If you used a different label name in Step 1, change it here.

Step 6 Test the full round trip

1. Have a colleague or test account send a PO to your real [email protected] address.
2. Wait 15-30 seconds for the forward to propagate.
3. Check the dedicated Gmail. The message should appear with the purchase-orders label.
4. In Claude Desktop, ask "list my incoming POs". The PO should appear.
5. Ask Claude to draft the reply. Open the resulting draft in Gmail — confirm the From field shows [email protected] and NOT the dedicated Gmail.
6. Send the reply. The buyer receives it from your real domain.