RelayMailPricing

RelayMail vs a Zapier email-to-Slack zap

Posting email into a Slack channel is a classic Zapier zap: forward mail to an Email by Zapier address (or watch a Gmail search) and send each one to a channel with Send Channel Message. If you only need to see the email in Slack, that works.

Answering from Slack is where it gets harder. A zap has one trigger, so the reply direction is a second zap: Zapier's documented way to catch thread replies is the channel message trigger plus a filter, then Gmail's Reply to Email action, which needs the original email's thread. Zapier doesn't document a built-in link between a Slack thread and an email thread, so you store that mapping yourself. RelayMail does both directions and keeps the mapping for you.

RelayMail
Zapier
Email shows up in a channel
Yes, each email starts a thread
Yes, with Send Channel Message
Reply to the sender from the Slack thread
Yes, built in
A second zap (thread-message filter + Gmail Reply to Email)
Customer follow-ups land in the same thread
Yes, matched by email headers
Only if you store and look up the thread yourself (e.g. Storage by Zapier)
How fast email arrives
As it is forwarded
Email by Zapier is instant (Zapier notes delays may occur); Gmail triggers poll every 2 min on Professional
Price
From $15/month per inbox, 14-day trial
Free plan: 100 tasks/month, two-step zaps only. Professional from $19.99/month billed yearly ($29.99 monthly) for 750 tasks

What a two-way zap setup needs

Zap 1 (email to Slack): a trigger on new email, then Send Channel Message. To make later replies possible you also save which Slack thread belongs to which email, for example with Storage by Zapier, which holds up to 500 keys per store and deletes keys after two months of inactivity.

Zap 2 (Slack to email): New Message Posted to Channel, a Filter step so only thread replies continue, a lookup of the saved email thread, then Gmail Reply to Email. Zapier warns that auto-reply workflows posting back into the thread they watch can loop and use up tasks, and thread replies don't show up as test samples while you build it.

Every successful action is a task, so each email and each reply uses several tasks across the two zaps.

Where email comes in

Email by Zapier gives you a custom @zapiermail.com address. Zapier's limits: messages under 10 MB including attachments, a sender address is required, and Zapier says delays may occur. Gmail's New Email triggers are polling triggers and only pick up email from the last hour.

RelayMail gives each inbox its own forwarding address, and the reply goes out from your own address once your domain is verified (Email by Zapier itself cannot send from a custom From address).

When Zapier is the better pick

  • ×You only want email to show up in Slack, with no replies from the channel.
  • ×You already pay for Zapier and want the email step inside a larger workflow (CRM updates, tickets, spreadsheets).
  • ×You only need emails to show up in Slack, not replies, and get under 100 a month: a one-way two-step zap fits Zapier's free plan (Gmail triggers check every 15 minutes there).

When RelayMail is the better pick

  • ✓You want to answer customers from the Slack thread without building and maintaining two zaps and a thread lookup.
  • ✓You want customer follow-ups to land in the same thread automatically.
  • ✓You want one flat price per inbox instead of counting tasks per email and reply.

Questions

Can Zapier send a Slack thread reply back as an email?

Yes, with a second zap: Zapier documents catching thread replies with the channel message trigger and a filter, and Gmail has a Reply to Email action. Matching the Slack thread to the right email thread is up to you; Zapier doesn't document a built-in mapping.

How many Zapier tasks does an email-to-Slack zap use?

Each successful action counts as one task; triggers and filters do not. A one-way zap uses at least one task per email, and a two-way setup uses more for each reply.

Can I forward email to Slack with Zapier for free?

One way, yes: Zapier's free plan has 100 tasks a month and two-step zaps, which is enough for a new-email trigger plus a Send Channel Message action. Replying from Slack takes a zap with a filter and a thread lookup, which is more than two steps, so it needs a paid plan.

Does RelayMail need Zapier?

No. You forward the address to RelayMail, connect a Slack channel, and replies from the thread go out as email.

Try RelayMail on your real inbox for 14 days

$0 today, then from $15/month per inbox. Cancel in Billing before day 14 and you pay nothing.

See plans and start the trial

Updated 2026-11-08. How we check these pages. Sources:

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