MailBrother
Add to Chrome
Documentation

Allow MailBrother in Google Workspace ("This app is blocked")

Google Workspace organisations can restrict which third-party apps may access Gmail and Google Sheets. When that setting is on, users see "This app is blocked" or "Access denied" while signing in to MailBrother. Personal @gmail.com accounts are never affected.

Only a Workspace administrator can change this. If you are not the admin, forward this page to the person who manages Google Workspace in your company.

Allow MailBrother (about two minutes)

  1. Open the Google Admin console → Security → Access and data control → API controls → Manage third-party app access.
  2. Click Add app → OAuth App Name or Client ID.
  3. Search for MailBrother, or paste the client ID below, and select the app.
  4. Choose the organisational units that may use it (or the whole organisation).
  5. Set access to Trusted: Can access all Google services and save.

MailBrother's OAuth client ID:

340053589582-966pi6uopslahkug2dnng6kik4d1o4em.apps.googleusercontent.com

Changes take effect within a few minutes. The user then clicks Sign in in the MailBrother menu again.

What the app asks for and why

ScopeUsed for
gmail.modifyReading the draft you wrote, sending one copy per recipient from your address, checking bounce replies, creating the "MailBrother" label for campaign copies.
userinfo.profileShowing which account is signed in.
spreadsheets.readonly, drive.readonlyOnly when you import recipients from a Google Sheet: listing your sheets and reading the selected one.

MailBrother never reads your inbox for anything but bounce notifications of your own campaigns, and never sends email you did not start. Data handling is described in the privacy information.

Restricting who can use it

You can allow the app for a single organisational unit (for example, Sales) and keep it blocked elsewhere. Daily sending is limited by Google to about 1,800 emails per Workspace user; MailBrother also lets you set a delay between emails and splits large lists across days.

Still blocked?

  • Check Security → API controls → Settings: if "Block all third-party API access" is on, the trusted-app list is ignored.
  • Some organisations also restrict Chrome extensions in Devices → Chrome → Apps & extensions; allow the MailBrother extension there.
  • Write to [email protected] with a screenshot of the error and we will help.