For agencies
Don't build your own email router.
You are about to wire Gmail to Slack. A Zap, a weekend script, a custom worker. Don't. The filter, the route, and the audit log already exist.
An agency inbox is not a personal Gmail tab. Client mail, vendor invoices, legal notices, and school or ops alerts land in a shared account. Someone always wants a notifier: ping Slack when this sender writes, dump the rest into a digest.
The first version is Zapier. The second is a script that refreshes tokens. The third is a worker you now own—matching, retries, and six destination formats. None of that is the work you sell.
The product you are accidentally building
Sending and routing is not an agency product.
OAuth, filter syntax, provider quirks, and “why didn’t this hit Teams?” support become yours the moment you ship a custom pipeline. That is infrastructure. Buy it.
Posthaste connects Gmail or Outlook, lets you write unlimited filters, summarizes what is worth interrupting a human for, and routes it to Slack, Teams, Discord, Telegram, Google Chat, and Matrix. You get CSV and JSON audit export. One plan: Posthaste Pro, $19/month per workspace.
What to do instead
Buy the router. Keep the agency.
If a sprint is about to go into sending mail to chat, stop. Subscribe, connect an inbox, and write the filters your team actually needs. How agencies use Posthaste · Pricing.