Zoho Mail Signature Deployment Setup

How to push your AdtoSign-managed email signatures into your Zoho Mail users' mailboxes. AdtoSign sets each user's Zoho Mail signature for them via the Zoho Mail API, using a one-time, admin-consented connection to your Zoho organization.

Status: Rolling out in phases — contact AdtoSign support to enable it for your organization. This guide documents the setup and limitations.

Audience: Zoho Super Admin / Org Admin. Your employees must already be synced into AdtoSign (Directory) and assigned a master signature (Signatures → master signature → assign users).

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How it works

Unlike Google Workspace (which offers two modes), Zoho is single-mode: AdtoSign holds a per-organization, admin-consented OAuth refresh token and writes each user's Zoho Mail signature through the Zoho Mail API. There is no customer-run-script option because Zoho has no Apps-Script-equivalent surface.

AdtoSign writes to a managed signature slot named "AdtoSign - Managed Signature" and promotes it to the user's default. Your users' other personal signatures are left untouched. The signature uses hosted image URLs (small HTML), so banner swaps propagate with no re-push.

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Setup

1. Pick your data center. In AdtoSign, open Directory → Connections → Zoho and select your Zoho data center — this MUST match where your Zoho account lives:

   Data center	Region
   com	United States (default)
   in	India
   eu	Europe
   com.au	Australia
   jp	Japan

   The data center controls both the sign-in endpoint (accounts.zoho.<dc>) and the Mail API (mail.zoho.<dc>). Picking the wrong one fails authorization.

2. Authorize AdtoSign (OAuth consent). Click Connect Zoho and sign in as an org admin. Grant the requested scopes:

   • ZohoMail.organization.accounts.READ — resolve each user's mailbox account
   • ZohoMail.settings.signatures — set the managed signature
   • ZohoPeople.users.READ — read your user list (directory sync)

3. Sync your directory (if not already) so AdtoSign knows your users, and assign each user a master signature.

4. Deploy. Open Signatures → Deployment → Zoho and click Deploy now (or wait for the next scheduled run). Per-user success/failure appears in Deployment → Logs.

Test first (recommended): deploy to a single pilot mailbox before rolling out to the whole org.

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How it runs

• AdtoSign fans out per user with automatic retries, and re-syncs nightly to repair drift (a user who manually changed their Zoho signature is restored on the next run). Per-user status appears in Deployment → Logs.

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Limitations

• Replies: whether the signature appears on replies is gated by a per-user Zoho setting the API cannot fully write. AdtoSign's deploy requests above-quote placement (position: 1), but Zoho's "Signature in Replies" toggle (Settings → Signature settings, bottom) is user-side only — if it's off, replies send unsigned until each user enables it once by hand. Orgs that need guaranteed reply signatures should use the mail-flow gateway, which inserts signatures server-side on every send.
• Mobile native app: the Zoho Mail app on iOS/Android keeps its own signature and does not reliably apply the managed signature to mail composed in the app. Zoho web works. This is a Zoho limitation.
• Not tamper-proof: a Zoho Mail signature is user-editable — a user can change or delete it. The nightly drift re-sync restores it, but between runs it can differ. (For guaranteed signing use the Outlook add-in / transport-rule path on Microsoft 365.)
• Data-center specific: the connection is bound to the data center you selected. If your Zoho org moves data centers you must reconnect.
• Overwrite: deployment replaces the managed signature slot ("AdtoSign - Managed Signature") and promotes it to default. Users' unrelated personal signatures are left alone.

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