---
title: "Cold email deliverability guide"
description: "Keep cold emails out of spam: set up SPF, DKIM and DMARC, use a secondary domain, warm up mailboxes, cap volume and write emails that land."
url: https://prosyo.com/docs/help/email-deliverability-guide/
section: "Help"
updated: 2026-11-06
---

# Cold email deliverability guide

Make sure your outreach emails land in the inbox, not spam. This guide covers domain setup, warm-up, volume and content.

## 1. Authenticate your domain

| Record | What it does | Where to set it |
|---|---|---|
| **SPF** | Lists the servers allowed to send for your domain | DNS TXT record, for example `v=spf1 include:_spf.google.com ~all` for Google Workspace |
| **DKIM** | Cryptographically signs your emails | Generated in your email admin, added as a DNS TXT or CNAME record |
| **DMARC** | Tells receivers what to do with failing mail | DNS TXT at `_dmarc.yourdomain.com`, for example `v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com` |

Gmail and other large mailbox providers require SPF, DKIM and DMARC for bulk senders. Check your setup with a free DNS or email-testing tool before you send.

**Where to find DKIM:**
- **Google Workspace:** Admin console → Apps → Google Workspace → Gmail → Authenticate email
- **Microsoft 365:** Microsoft Defender → Email & collaboration → Policies → Email authentication settings → DKIM
- **Zoho Mail:** Mail admin → Domains → Email configuration
- **Other providers:** look for DKIM in your mail host's domain or authentication settings

## 2. Use a secondary domain

Send cold outreach from a domain like `getacme.com` or `tryacme.com` instead of `acme.com`. If something goes wrong, your main domain, and your team's everyday email, stays safe.

- Redirect the secondary domain to your main website.
- Set up SPF, DKIM and DMARC on it too.
- Create real mailboxes with real names, for example `priya@getacme.com`.

## 3. Warm up new mailboxes

| Week | Emails / day per mailbox |
|---|---|
| 1 | 5–10 (to people you know) |
| 2 | 15–25 |
| 3 | 25–40 |
| 4+ | Up to 50 |

In Prosyo, set **Emails / day** on the campaign's **Sending & safety** tab. The limit applies to each mailbox. The **Cautious** preset starts at 25.

## 4. Keep volume per mailbox low

Stay under about **50 cold emails per mailbox per day**. For more volume, add mailboxes rather than pushing one harder:

- **Extra SMTP/IMAP seat:** $2 (€2, ₹149) a month per mailbox, on Multichannel, Agency / Team or AppSumo plans. See [Add-ons](https://prosyo.com/docs/billing/add-ons-and-upgrades.md).
- Pick several mailboxes under **Sending & safety → Email accounts** (up to 10 per campaign). Each person stays with one mailbox, so replies stay in one thread.
- Or split the list across campaigns, each with its own mailbox.

## 5. Write emails that land

| Do | Don't |
|---|---|
| Plain text | Heavy HTML, images, attachments |
| Under 120 words | Long paragraphs |
| One link at most (or none in email 1) | Several links or link shorteners |
| A natural subject line: `{{company_name}} + outbound` | "FREE", "Act now", ALL CAPS, lots of !!! |
| Personalization that's real | Obvious mail-merge ("Dear {{first_name}}") |
| Replies in the same thread for follow-ups | A new subject every time |

## 6. Keep your list clean

- Only email addresses from a real source. Prosyo never guesses emails.
- Verify addresses from data providers before importing.
- Remove bounces and people who ask to stop. Suppress them: **DNC** on their conversation in Inbox, or **Suppress** on **Prospects**.

## 7. Watch the signals

| Signal | Healthy | Act if |
|---|---|---|
| Bounce rate | Under 2% | Over 3%: clean your list |
| Reply rate | 2%+ | Under 1%: check spam placement and targeting |
| Spam complaints | ~0 | Any: slow down, review copy and targeting |

## 8. Compliance

Follow the laws where your recipients are, such as CAN-SPAM, GDPR, PECR and CASL. Identify yourself, have a legitimate reason to contact them, and honor opt-outs immediately. See [Responsible outreach](https://prosyo.com/docs/help/responsible-outreach.md).

## Quick checklist

- [ ] SPF, DKIM and DMARC pass
- [ ] Secondary sending domain
- [ ] Mailbox warmed for 2+ weeks
- [ ] Under 50 cold emails per mailbox per day
- [ ] Plain text, one link at most, under 120 words
- [ ] Clean, verified list
- [ ] Opt-outs suppressed (Do not contact)