Warming Up a New Sending Domain

Why new domains need warming up

Mailbox providers (Gmail, Outlook, Yahoo, etc.) don’t trust email from a domain they’ve never seen before. A brand-new sending domain has no sending history and no reputation: so if you connect it and immediately blast thousands of emails, providers often assume it’s spam and start bouncing or filtering your messages, even if your content and list are perfectly fine.

“Warming up” means starting with small sending volumes and gradually increasing them over time, so mailbox providers can observe good engagement (opens, clicks, no complaints) and build trust in your domain before you send at full volume.

Step 1: Set up your Sending Domain correctly

Before sending anything:

1. Go to Organization → Sending Domains and add your domain.
2. Use a subdomain, not your root domain – e.g. mail.yourdomain.com or send.yourdomain.com, not yourdomain.com.

• This avoids conflicts with SPF records your regular business email (Google Workspace/Microsoft 365) already uses.
• It keeps your bulk-campaign sending reputation separate from your everyday email reputation: if a campaign has issues, it won’t affect your regular business email.

3. Add the SPF and DKIM DNS records shown in the dialog, and verify the domain.
4. You do not need a separate DMARC record for the subdomain; DMARC checks automatically fall back to your root domain’s policy if the subdomain doesn’t have its own.

Step 2: Turn on Gradual Send for your first campaigns

When creating a campaign, you’ll see a Gradual Send option (marked “Optional”) in the campaign setup. Turn this on for at least your first few sends from a new domain.

Configure three things:

Setting	What it does	Recommended for a brand-new domain
Starting rate	Emails sent per minute at the very start	Low – 1 to 60/min
Ramp duration	How long it takes to climb from the starting rate up to your full Sending Rate	Longer is safer – 24h, 48h, or 72h presets are available (up to 168h/1 week)
Safety threshold	Auto-pauses the campaign if bounce/complaint rates spike	Start with Conservative or Balanced

Once enabled, SureContact automatically increases your send rate on a straight-line ramp from the starting rate up to your campaign’s Sending Rate over the ramp duration you chose; no manual adjustment needed.

Safety thresholds (auto-pause)

Preset	Bounce rate limit	Complaint rate limit
Conservative	2%	0.05%
Balanced (default)	3%	0.07%
Aggressive	5%	0.1%

If bounce or complaint rates cross the chosen limit while sending, the campaign automatically pauses and the workspace owner gets both an in-app notification and an email. This protects your new domain’s reputation from a bad list or a content issue before it does real damage.

• Bounce rate is checked once at least 50 emails have been sent.
• Complaint rate is checked once at least 1,000 emails have been sent (complaints need a bigger sample to be meaningful; one early spam click on a small batch isn’t a real signal).
• Resuming a paused campaign is always manual; SureContact won’t auto-resume, so you get a chance to review your list or content first.

You can watch live progress (current send rate, ramp progress, bounce/complaint rates vs. thresholds, estimated completion time) on the campaign detail page while it’s sending.

Step 3: What to tell customers who ask “why is this so slow?”

Explain that the slower ramp is intentional and protective:

• Sending too fast on a new domain is what gets flagged as spam in the first place.
• A longer ramp gives mailbox providers more time to see good engagement and gives SureContact’s bounce/complaint webhooks more time to catch problems before they snowball.
• It’s a one-time cost; once a domain has a positive sending history, Gradual Send isn’t required for future campaigns (though it can still be left on as a safety net).

Emails Going to Spam for a New Domain:

If your test email campaigns are landing in the Spam folder, this is common when sending from a new domain with no established sender reputation.

To help improve deliverability:

• Mark the email as “Not Spam” in your inbox.
• Repeat this process for the next 1–2 test campaigns.
• As your domain builds a positive reputation, future emails are more likely to be delivered directly to the Inbox instead of the Spam folder.

Quick troubleshooting

Symptom	Likely cause	What to check
Campaign auto-paused right after launch	Bounce/complaint threshold breached	Check the pause reason on the campaign – “bounce rate” points to a bad/old list, “complaint rate” points to content or targeting issues
Emails going to spam despite warmup	DNS not fully set up	Confirm SPF/DKIM show verified on the Sending Domain; confirm they used a subdomain, not the root domain
Existing business email breaks after adding SMTP	Root domain used instead of subdomain, or SPF record replaced instead of merged	Check the domain string on their Sending Domain – if it’s the apex domain, that’s the likely cause