Sender reputation and domain warming for Indian email marketers

Every domain that sends email has a reputation. Gmail, Outlook, Yahoo, and corporate mail servers all maintain scores for sending domains based on historical behaviour. A high reputation means your emails reach the inbox. A low reputation means spam folders, or rejection.

Most Indian businesses do not think about sender reputation until something goes wrong. Emails stop reaching customers. A festival campaign underperforms. Open rates collapse without explanation. Almost always, the root cause is a reputation problem that built up over months.

How sender reputation is calculated

Inbox providers weigh multiple factors. Engagement is the biggest signal: the ratio of opens, clicks, and replies to total emails sent. If you send 10,000 emails and only 200 people open them, your engagement rate is 2%. That is not great. If 500 of those 10,000 hit spam addresses or bounce, that is a problem.

Complaint rate matters enormously. Every time someone marks your email as spam in Gmail, Google records it against your domain. A complaint rate above 0.1% triggers filtering. Above 0.3% and Gmail starts blocking you at the infrastructure level. Indian businesses running purchased lists or not cleaning their lists regularly often hit these thresholds without realising it.

Volume consistency matters too. Sending 200 emails per day for three months and then suddenly sending 50,000 in a single day looks suspicious. Inbox providers see it as behaviour inconsistent with a legitimate sender.

Domain warming: what it is and why it matters

Domain warming is the process of gradually increasing your email volume from a new domain or IP address over several weeks. The goal is to establish a pattern of legitimate, engaged sending before you scale.

A typical warming schedule for an Indian business starting fresh:

Week 1: send to 250 to 500 of your most engaged subscribers (people who have opened emails in the last 30 days). Week 2: increase to 1,000 to 2,000. Week 3: 4,000 to 6,000. Week 4: 10,000 to 15,000.

Continue doubling roughly every week until you reach your target volume. At each stage, monitor bounce rates and complaint rates carefully. If either spikes, slow down the warmup.

Choosing the right subscribers for warmup

The warmup period is not the time to test re-engagement with old inactive subscribers. Use your best list. People who have opened or clicked your emails in the last 60 to 90 days are ideal. Their engagement during the warmup period signals to inbox providers that you are a legitimate sender whose recipients want to hear from you.

Save the re-engagement campaigns and list cleaning for after the warmup is complete.

Separating transactional and marketing email

Transactional emails, such as order confirmations, OTP messages, shipping updates, have naturally high engagement rates because recipients expect and need them. Marketing emails like newsletters and promotional campaigns have lower engagement.

Mixing them from the same domain and IP can drag your transactional email deliverability down if your marketing engagement is poor. Indian businesses with any meaningful e-commerce volume should send transactional emails from a separate subdomain (like transact.yourdomain.com) and marketing emails from another (like news.yourdomain.com). This keeps the reputations separate.

Tools to monitor your reputation

Google Postmaster Tools is free and shows your Gmail-specific domain and IP reputation on a scale from bad to high. Set it up for any domain you send significant volume from.

Microsoft's JMRP (Junk Mail Reporting Program) gives equivalent feedback for Outlook and Hotmail recipients.

MXToolbox and Sender Score give broader reputation signals and check whether your sending IP appears on any blacklists.

Frequently asked questions