Email sending volume and warm-up

Your sender reputation is the track record that mailbox providers build for your store based on how subscribers interact with your emails. You might need to warm up your sender reputation in the following situations:

• You're new to sending email marketing.
• You're sending from a new domain.
• You're switching to Shopify Messaging from another email marketing platform.
• You're sending email marketing messages after a long gap.

In each of these cases, email providers have little recent history for your store. Providers are more likely to defer, throttle, or filter messages from an unrecognized sender, especially in large volumes. Warming up means starting small with the subscribers most likely to engage, then expanding gradually as providers learn to trust you.

Before you start warming up, authenticate your sending domain if you use a custom domain. Gmail and Yahoo require authentication, and unauthenticated email is more likely to be filtered. Authentication can take up to 48 hours to verify after you add the required records.

Cleaning your list before you send

Bounces and spam complaints during a warm-up have the greatest impact on your reputation, because providers are forming their first impression of your domain.

Before your first send, make sure that your subscriber list includes only valid addresses from subscribers who opted in. For specific list-cleaning practices, refer to Maintaining a high-quality subscriber list.

You can also review your list for suspicious patterns, such as subscribers with unusual email domains who have never opened a message or made a purchase. For more ways to prevent bot signups, refer to Preventing bot-generated subscribers.

Importing your engagement history when you migrate from another provider

If you're switching to Shopify Messaging from another email platform, then your sender reputation doesn't transfer, but your subscribers' engagement history can help you start strong. Before you migrate, export as much of the following as your previous provider allows:

• Consent and acquisition data: When and how each subscriber opted in.
• Engagement history: Opens, clicks, recent purchases, unsubscribes, bounces, and spam complaints.

You can import your customer list into Shopify using a CSV file. Use your engagement history to sort your contacts. Subscribers who opened or clicked recently are your safest first sends. Contacts who bounced, complained, or unsubscribed shouldn't be migrated.

Handling subscribers with unclear consent

If you can't confirm how or when a contact opted in, then leave them out of the warm-up entirely until your reputation is established. Sending to subscribers who don't remember signing up is a common cause of early spam complaints.

After your reputation is stronger, you can send a single, clearly worded opt-in email to those contacts and add anyone who confirms back to your active list.

Starting with your most engaged subscribers

Begin your warm-up with the subscribers most likely to open and click, then widen your audience over time. Strong early engagement is the most important signal you can send to providers.

Use customer segments to target engaged contacts. You can also browse segment templates for ready-made options. The following segments are good starting points for a warm-up:

• Subscribers who opened or clicked an email in the last 3 months
• Subscribers who opened emails recently and spent a certain amount
• Subscribers who recently made a purchase
• Subscribers who were added recently and have placed an order

Send to your most engaged segment first. As your open and click rates hold steady, expand to broader segments one step at a time. If your metrics drop, then pause and stay at your current audience size until they recover.

Giving early sends a reason to engage

The faster you generate opens and clicks, the faster you build trust with providers. Lead your warm-up with content that subscribers want to act on:

• Add a strong offer to your welcome automation, such as store credit or a discount code, so that new subscribers engage right away. To learn more, refer to Marketing automations.
• Send an occasional high-interest campaign, such as a sweepstakes, early access, or a standout promotion, to your engaged segments to lift opens and clicks.

Keep the frequency low as you warm up. A few well-targeted, high-engagement sends do more for your reputation than a large, generic campaign.

Ramping your volume gradually

Increase how much you send in small, steady steps rather than all at one time. For a recommended ramp schedule, refer to Increasing your email volume gradually.

Monitoring your results as you warm up

Watch your results closely during a warm-up so that you can slow down before a problem grows. Review each campaign's email analytics for delivery rate, open rate, click rate, bounce rate, and spam rate.

Mailbox providers also offer free tools that report how they score your sending domain, which your in-admin reports can't show. For details on setting up these tools, refer to monitoring your delivery metrics.

Slow down or pause your warm-up if you notice rising bounces, rising spam complaints, or falling open rates. Return to the audience size that last performed well, and expand again only after the numbers recover.

After your reputation is established, sudden changes in volume are the most common cause of blocks and delays, even for trusted senders. Providers monitor your sending patterns and take action when you send too much too quickly. They might defer messages, throttle delivery, route more messages to spam or promotions folders, or temporarily block sends.

Practices that can trigger blocks

The following practices can cause providers to block or delay messages until they verify that you're a legitimate sender:

• Sending 5 times your normal email volume in a single day.
• Long gaps in sending followed by large email campaigns.
• Sudden spikes in sending without gradual increases.
• Poor list quality, such as sending to subscribers who haven't engaged in a long time, who never opted in, or who don't remember opting in. To learn more, refer to Maintaining a high-quality subscriber list.

For example, if you typically send 2,000 emails per day and suddenly send 10,000 in one hour, then providers might deliver the first batch and defer or throttle the rest, so some messages arrive hours or days later, or don't deliver.

Signs of volume-related delivery issues

If you notice any of the following signs, then volume spikes might be impacting your deliverability:

• Emails to Gmail, Yahoo, or Outlook are delayed by hours or days
• Sudden drop in open rates for specific mailbox providers
• Subscribers reporting that they didn't receive your email campaign
• Increased spam folder placement

Tips for maintaining consistency

Review the following practices for maintaining volume consistency and avoiding blocks and delays:

• Monitor your spam complaint rate and keep it low to avoid blocks.
• Send emails on a regular schedule, such as daily, weekly, or bi-weekly, and keep your volumes similar from send to send.
• Avoid long gaps between email campaigns followed by large sends.
• Focus on engaged subscribers first. For list quality and segmentation tips, refer to Maintaining a high-quality subscriber list.
• When you need to increase volume, do it gradually. To learn more, refer to Increasing your email volume gradually.

If you need to increase your email volume to send to more subscribers, then do so gradually using the following guidelines:

• Increase your send volume by 20–30% each week until you reach your target volume. Avoid increasing by more than 30% per week, even if you have an established sender reputation. To learn more about safe increases, refer to Gmail's email sender guidelines. The same principle applies to other providers.
• Monitor your delivery metrics, such as open rates, click rates, and spam complaints as you increase volume.
• Continue increasing volume each week until you reach your target. If your delivery, open, and click rates drop, then hold at your current volume until they recover.

For example, if you currently send 5,000 emails per week and want to reach 17,500, then plan for a 6-week ramp-up:

Example 6-week volume ramp from 5,000 to 17,500 emails per week at roughly 25–30% growth each week

Week	Volume	Increase
1	5,000	Baseline
2	6,500	+30%
3	8,500	+30%
4	11,000	+30%
5	14,000	+27%
6	17,500	+25%

When a campaign is larger than your usual volume or you send only one time per month, spread sending across multiple days or throughout the day so that email providers don't treat it as a volume spike and delay or block delivery.

Approaches to sending your large campaign consistently

Consider any of the following approaches when sending a large campaign to prevent volume spikes:

• Same volume each day: Send a consistent number per day so email providers recognize your volume as normal. For example, 5,000 emails per day over 4 days instead of 20,000 in one day, or 5,000–7,000 per day over 3–4 days.
• Smaller batches at set times: Send to portions of your list at different times across one or two days. For example, 25% in the morning, 25% in the afternoon, 25% the next morning, and 25% the next afternoon. This keeps hourly send rates manageable.
• Micro-batching at regular intervals: Send smaller batches at regular intervals throughout the day. For example, 2,500 emails every 2 hours instead of 20,000 in one send (eight sends over 16 hours, 1–2 days). This helps email providers recognize a consistent hourly pattern.

Any of these approaches reach your full audience and help prevent blocks.

Monthly sending best practices

If you send only one time per month, then apply one of the following approaches that work well for a monthly cadence:

• Same-day segmentation: Send to 25% of your subscriber list every 6 hours throughout the day.
• Multi-day approach: Send to 50% of your list on Day 1 and the remaining 50% on Day 2.
• Extended timeline: Divide your list into 3–4 segments and send one segment per day over 3–4 days.

Plan ahead for seasonal events such as Black Friday, Cyber Monday, holiday sales, and other events that require you to email more subscribers than usual. Start increasing your volume at least 4–6 weeks before your campaign to establish the new pattern.

For example, if you normally send 5,000 emails per week but need to send 15,000 for a seasonal campaign, then increase your send volume as follows:

• 6 weeks before: Start at your current baseline of 5,000 emails 6 weeks ahead of time.
• Weeks 1–5: Increase your send volume by 20–30% each week.
• Campaign week: Send at your target volume of 15,000.

This gradual approach gives email providers time to recognize the increase as legitimate growth.

If your emails are being blocked or delayed after a volume spike, then take the following steps to restore your sender reputation:

• Reduce your send volume to your previous baseline or lower.
• Send only to your most engaged subscribers, such as those who opened or clicked in the last 30 days. To learn more about targeting engaged subscribers, refer to Maintaining a high-quality subscriber list and Customer segments.
• Maintain consistent sending for several weeks to rebuild trust with email providers.
• Gradually increase volume using the 20–30% weekly increase when your metrics stabilize.

Recovery typically takes several weeks. You'll know that your delivery is improving when emails reach inboxes within minutes, open rates return to normal, you experience fewer deferrals or "try again later" responses, and subscribers report receiving your campaigns.