Warming up a domain for sending emails is an important step when you use a newly registered domain or if the domain was never used for sending emails. This process establishes your sending reputation and improves email deliverability. The warm-up itself involves gradually increasing your email sending volume to build trust with email service providers (ESPs) and avoid being flagged as spam. Otherwise, there’s a significant risk that email service providers (like Gmail, Yahoo, Outlook, etc.) will treat your domain as suspicious since it has no sending reputation yet and would reject emails from you or mark them as spam.
NOTE: On our side, as an email service provider, we do everything possible to maintain good deliverability of your emails, e.g. keeping our IP addresses clean by having 24/7 IP addresses monitoring and promptly communicating with blocklist organizations to delist our IP addresses if that happens, we constantly monitor any spam activity on the servers and take necessary measures, etc. At the same time, some factors affect your email deliverability that we cannot influence due to their nature. This includes your domain reputation (involving whether your domain is warm), your email content, actions with the email on the recipient’s side, etc.
Here are recommendations for manually warming up a domain name for better email deliverability:
Start with a clean domain
If your domain isn’t newly registered and has been previously used, it's necessary to check if the domain is present in any blocklists and clean it up before starting to send emails regularly. It’s important since email service providers may simply reject emails sent from a blocklisted domain.
Some blocklists can unblock your domain automatically after some time, so you don't have to do anything (e.g. SpamCop usually delists domains after 24 hours). On the other hand, some other blocklists may take more time and information to put you on their list as they often use information from various RBLs and spam filters to label a sender as suspicious. Therefore, if you end up on one of those blacklists, the process may be a bit more complex and you'll need to reach out to them to get your domain removed manually. Many blocklists usually have the necessary information on their websites about how to delist your domain, so you may refer to their websites or contact their support team if this is the case.
You can use tools like MultiRBL and MXToolbox to verify whether your domain is present in any blocklists and to check your domain’s general reputation score.
Check how old your domain is
Newly registered domains are usually marked as suspicious by spam filters as they assess the age of a domain: if it is less than 30 days, the domain is automatically flagged as suspicious and emails originating from it will likely be rejected or placed in the Spam folder. Therefore, if your domain is less than 30 days old, being ready for the warm-up process is especially required in this case to build trust with email service providers. As your domain reaches 30 days, there's less chance that you face deliverability issues or possible rejects with your emails.
NOTE: You can check when your domain was registered using Whois Lookup tools, like this one.
Verify domain DNS settings
You will need to make sure that your domain has the correct MX records set so that you can receive emails. Then, ensure your domain's SPF, DKIM and DMARC records are correctly configured. SPF authorises servers allowed to send emails on behalf of your domain, DKIM verifies the authenticity of outgoing messages, and DMARC helps protect your domain from spoofing and phishing attempts. All in all, these records are responsible for email authentication and are designed to help prevent email spoofing and phishing attacks. You can check more information about these DNS records in this guide.
For Spacemail, follow the steps in these articles to configure DKIM and DMARC records for the domain. The full list of required Spacemail DNS records are provided in this Knowledge base article.
Use a recognisable "From" name
Make sure to set both your First/Last name or Company name to be displayed in the "From" field and a signature to make your emails look valid and more personalised.
Use non-spam content for emails
- Ensure your messages do not contain suspicious links or attachments;
- Avoid using formatting, such as all capital letters (e.g. OPEN), letters with spaces between them (e.g. O P E N), and excessive punctuation (e.g., O.P.E.N);
- Avoid sending blank or one-word emails;
- Make sure you don’t use such words as ‘test’, ‘testing’, ‘test test test’, ‘hello’, ‘hi’ both in the message body and subject lines;
- Avoid using common spam trigger words both in the message body and subject lines (e.g. 100% free, winning, urgent, cure, loan, luxury, investment, become a member, prize, etc.).
Your messages should contain at least 5-6 sentences with full words (without random sequences of letters) and it has to be different every time (otherwise, email providers may treat it as mass mailing).
You can check more recommendations in this guide: Why emails go to spam and what to do
Start gradually sending emails
In the beginning, you may need at least 5 email addresses with different email providers to send the messages to (e.g. AOL, Yahoo, Gmail, Hotmail, Outlook, etc.). You may send emails to familiar email addresses (just ask the recipients to engage with your emails) or your own email addresses with different email providers.
Begin by sending a low volume of emails during the first days of your warm-up process and gradually increase the number of emails you send weekly. Sending excessive amounts of emails too quickly may result in being flagged by anti-spam filters. Here is a possible schedule you can follow:
Week 1: 10 emails
Week 2: 30 emails
Week 3: 80 emails
Week 4: 100 emails
Week 5: 150 emails
Week 6: 200 emails
Please note that this is just an approximate scheme and you may not follow it strictly, but just make sure that you don’t increase or decrease volumes abruptly.
Spacemail, like every email provider, enforces hourly/daily sending limits. You can check them here:https://www.spaceship.com/knowledgebase/spacemail-email-limits/
Domain warm-up is allowed when done manually and responsibly, for example, by gradually increasing your sending volume with genuine, opt-in recipients. However, automated warm-up tools, simulated engagement networks, or unverified mailing lists are not permitted, as such activity may harm overall deliverability and affect other users.
Please also keep in mind that our email services are not designed for mass mailing. Any unsolicited commercial, bulk, or automated email activity is prohibited under our zero-tolerance spam policy. For details, review the Acceptable Use Policy -https://www.spaceship.com/legal/hosting-aup/ - and the Spacemail Terms of Service - https://www.spaceship.com/legal/spacemail/
NOTE: Spaceship, like every email service provider, has specific hourly and daily limits on the number of messages users can send. You can check them here.
Please take into account that our services are not designed for mass mailing and you may want to use some other special tools for this purpose. In addition, any unsolicited commercial or bulk mail is prohibited on our servers as we have a zero-tolerance spam policy. You can check our Acceptable Use Policy, Email and Anti-spam Policy section.
Maintain engagement
Once you're done with sending out emails, it's very important to reply to all of them so that email providers learn that the messages you send are legitimate and non-spam. Reply rate is especially important for Gmail as they use it to determine email engagement. The higher the engagement - the better.
When replying to emails, try to maintain a natural approach and reply as you normally would during any other correspondence so that it sounds neutral. If some emails were marked as spam/junk by the email provider, it's essential to mark them as not spam and move them to the Inbox folder. You may also ask the recipients to mark your email as important.
This way when your emails are opened replied to, and engaged with, these are signals for email service providers that your domain is reputable. Over time, if you maintain such an approach, you will notice that fewer and fewer emails are marked as spam by email providers. This usually happens after a few weeks after the start of a warm-up process. This is when you can proceed with sending your regular correspondence without high risks of your emails being marked as spam by the recipient's email providers.