Blacklists are lists of email senders who are known to send spam. These lists are maintained by internet service providers, anti-spam services, and mailbox providers. When it comes to offering inbox placement, mailbox providers give preference to emails from sender domains and IP addresses that are not blacklisted. A sender domain/IP address will get blacklisted when emails receive complaints, spam markings, unsubscribes, etc.

When your sender domain/IP address gets blacklisted, the emails you send will either bounce or land in the spam folder. We always recommend you verify the health of your sender domain using tools like MXToolbox before sending a campaign. 

If your sender domain/IP address gets blacklisted, is it the end of the road? Definitely not. When your sender domain/IP address gets blacklisted, we urge you to pause sending campaigns and resolve the issue as soon as possible. We recommend you resume sending emails only after your sender domain/IP address is delisted.

The best way to prevent your sender domain/IP address from getting blacklisted is by adopting hygienic email sending practices and maintaining quality mailing lists.

One of the major reasons for a sender domain/IP address getting blacklisted is when sent emails hit spam traps. Your emails may hit spam traps when you use purchased mailing lists. Also, mailbox providers use expired email addresses and unused email addresses as spam traps. So, it is always advisable to prune your mailing list every six months to ensure that the mailing list doesn't contain such spam traps.

The receiving servers of mailbox providers will scan the email content to identify patterns that point towards spam. If your emails contain spam phrases, blacklisted URLs, or shortened URLs, the receiving server may blacklist your sender domain/IP address.

After sending a campaign, you need to monitor its performance. If the campaign receives spam markings or unsubscribes, you need to perform a grassroots-level analysis and resolve the issue immediately. You need to adopt hygienic email marketing practices to prevent the issue from cropping up again. If you leave deliverability issues unresolved, they may lead to your sender domain/IP address address getting blacklisted.

If your mailing list contains a lot of inactive contacts, they might mark your emails as spam. So, we always recommend our users identify inactive contacts and win them back by sending re-engagement campaigns. While crafting re-engagement campaigns, use attractive subject lines, list the benefits of staying on your mailing list, offer discounts, and ask the contacts if they are interested in receiving your emails. You can retain contacts who decide to stay on your mailing list and remove contacts who don't respond to your re-engagement campaign.

The only way to prevent contacts from negatively engaging with your emails is by offering content that's relevant to their needs and interests. To do this, you need to analyze their purchase history and the links they clicked in your previous emails. Once you identify what your contacts are interested in, you can segment contacts based on their interests and start nurturing them. When you offer content that excites your contacts, they will look forward to receiving your emails and will not negatively engage with them.

Click here to learn more about keeping your contacts engaged.

The receiving servers of all mailbox providers have set a threshold value for emails they receive per hour/day. If your email volume exceeds the threshold value, the receiving server will reject your email and may even blacklist your sender domain/IP address. Hence we always urge businesses to maintain optimal email volume and frequency. We recommend businesses split their email volume and send them in batches.

At Zoho Campaigns, we have a feature for sending campaigns in batches. You can click here to learn more about this feature.

When you use the single-opt-in technique, invalid email addresses may get added to your mailing list. When you send emails to such addresses, your emails may bounce or hit spam traps. The only way to prevent this is by using the double-opt-in technique, which sends an initial follow-up email to the address asking the person to verify that they did indeed sign up for the mailing list. The double opt-in technique will ensure that only interested contacts enter your mailing list and prevent email bounces and spam trap hits.

Getting their sender domain/IP address blacklisted is the last thing marketers want. The only way to prevent a sender domain/IP address from getting blacklisted is by adopting hygienic email sending practices and keeping contacts engaged.