How to warm up a sender domain
We know that as marketers, you want to send large volumes of emails and achieve inbox placement. When mailbox providers receive emails, they consider the reputation of a sender domain to make inbox decisions. So, how is the reputation of a sender domain calculated? Mailbox providers use different techniques to grade the reputation of your sender domain. Some assign a score (0 - 100), while others rank reputations as "low," "medium," or "high." Here are the factors mailbox providers consider when grading a sender domain:
- Email volume
- Email engagement
- Spam markings and classification
- Spam trap hits
- Bounce rate
- Total complaints received
- Unsubscribe rate
Before sending an email campaign, make sure you're using a sender domain with a positive reputation. Otherwise, your emails may face deliverability issues. If you decide to increase the email volume or use a new sender domain, we recommend warming up the sender domain first. Warming up a sender domain is the process of earning a positive reputation from mailbox providers. It can't be done overnight. It is a methodical process that takes a couple of weeks.
Let's dive deep and learn how to successfully warm up your sender domain.
Warmup prerequisites
- Implement email authentication techniques like SPF, DKIM, and DMARC and update your records and domain keys. Click here to learn about authenticating your sender domain.
- Verify the "whois" record for the sender domain.
- Set up the Google Postmaster tool to gain insights about the reputation your sender domain has earned from Gmail.
- Clean your mailing list. Segment active contacts in your mailing list or build a new mailing list and add active contacts to it. This will be the mailing list you use during the warm-up process.
Warming up your sender domain
After you complete the prerequisites, you can begin warming up your sender domain. Warming up is the process of gradually increasing the email volume. When contacts engage with your emails, your sender domain earns a positive reputation. By the end of the warm-up process, your sender domain will be primed and ready to send any email volume you have planned.
Here's a table to help you plan your email volume throughout the warmup:
Day | Number of emails |
1 | 50 |
2 | 50 |
3 | 100 |
4 | 100 |
5 | 200 |
6 | 200 |
7 | 400 |
8 | 400 |
9 | 800 |
10 | 800 |
11 | 1,600 |
12 | 1,600 |
13 | 3,200 |
14 | 3,200 |
15 | 6,400 |
16 | 6,400 |
17 | 12,800 |
18 | 12,800 |
19 | 25,600 |
20 | 25,600 |
21 | 51,200 |
You can start the warm-up process by sending emails to active contacts first. Active contacts will engage with your emails, and help your sender domain earn a positive reputation. For the first two weeks of the warm-up process, we recommend sending emails to active contacts only. After the third week, you can slowly start sending emails to the remaining contacts.
Handling deliverability issues
If you face deliverability issues during the warm-up procedure, you should pause sending emails, identify the issue, and take necessary corrective measures. Here are some issues you may face and the best practices to resolve them:
When your email gets classified as spam
When mailbox providers or contacts mark your emails as spam, they negatively impact your sender domain's reputation. Here are some tips to prevent emails from getting marked as spam:
Subject line
- Don't capitalize the entire subject line
- Don't overuse punctuation marks
- Avoid using phrases like "cash bonus" and "cheap"
- Avoid using special characters like $, #, @, and
- Don't use fake Re/Fwd tags
Click here to learn more about crafting successful subject lines.
Spam phrases
When mailbox providers scan incoming emails, they look for spam phrases. If they find them, they may classify your emails as spam. Here are a few common spam phrases to avoid using in your emails:
- Make money
- F R E E
- Extra income
- Hidden
- Miracle
URLs
We urge our users not to use shortened URLs, blacklisted URLs, and URLs that direct email recipients to blacklisted domains. At Zoho Campaigns, we recommend sending your campaign to test accounts before sending it to your contacts. This will help you verify the campaign's content and ensure that the URLs work correctly.When the sender domain earns a negative reputation
If your emails hit spam traps, or contain blacklisted URLs or URLs of blacklisted domains, your sender domain will earn a negative reputation. In these situations, you need to pause the warm-up process, identify the issue, and take corrective measures. We recommend you wait to resume the warm-up process until the issue is resolved.
Temporary email deferral
Temporary deferral means the receiving server refuses to deliver your emails for the time being. Your emails will not be delivered until the issue that caused the deferral is resolved. During the warm-up procedure, if your emails are rejected due to a high sending rate, you must reduce your email volume. When you send the next batch of emails, your email volume should be at least half of what you last sent. You can slowly increase the email volume after successful email delivery.
Resuming the warm-up process after a pause
Let's say that you have been sending 25,000 emails per day during the warmup. Now you have stopped sending emails due to deliverability issues. After a few weeks of inactivity, if you resume the warm-up procedure by sending 25,000 emails, you will face delivery issues. Mailbox providers track the sender domain's email activity history and reputation. If you send 25,000 emails after a brief period of inactivity, mailbox providers will observe this sudden spike in volume. This will lead to delivery issues, such as email rejection. So, you should start sending 50 emails per day and slowly increase the email volume.
Best practices to warm up a sender domain
During the warm-up process, you must monitor the performance of the campaigns you send and keep tabs on the open rate, click rate, and bounce rate. Every now and then, you can run your sender domain through blacklists to ensure that it hasn't been blacklisted. When you warm up your sender domain, adopt hygienic email-sending practices such as considering your contacts' time zone and using the target marketing strategy. You can identify campaigns that performed well in the past and use them as models to get maximum email engagement. You can also use the A/B testing technique to identify the best subject lines for your campaigns.
Warming up a sender domain is not something that can be accomplished in a couple of days. It is a process that often requires a few weeks. The best way to warm up a sender domain is by adopting hygienic email-sending practices and gradually increasing your email volume.
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