15 Do’s and Don’ts to Avoid Having Your Email Blocked or Blocklisted
Bird
Jan 18, 2016
1 min read
Key Takeaways
Email blocklisting can happen even if you don’t intentionally send spam — poor practices alone can trigger it.
Purchased lists are one of the fastest ways to get blocklisted due to spamtraps and disengaged recipients.
Double opt-in helps guarantee real, valid signups and minimizes spam complaints.
Repetitive, vague, or misleading content increases complaint rates and damages sender reputation.
Attachments are commonly blocked at gateways and should be avoided in bulk or marketing campaigns.
Proper unsubscribe methods, sender identity, and subscriber trust signals significantly affect deliverability.
Sending frequency must be consistent but not excessive to maintain engagement and avoid filtering.
Strong list hygiene practices prevent bounces, protect reputation, and maintain healthy deliverability.
Avoid spammy signals such as excessive punctuation, all-caps, image-only messages, and BCC sending.
Securing your sending environment is essential — malware-infected servers can send spam without your knowledge.
Q&A Highlights
What causes an email to be blocked or blocklisted?
ISPs and anti-spam organizations maintain blocklists of IPs and domains associated with spam-like behavior. Poor sending practices, spamtraps, high complaint rates, and infected servers can all result in blocks—even for legitimate senders.
Why is buying email lists so dangerous?
Purchased lists often contain spamtraps, stale addresses, and people who never opted in. Sending to them leads to high complaint rates and almost guarantees blocklisting.
How does double opt-in help prevent blocklisting?
Double opt-in ensures subscribers confirm ownership of their email address. This reduces fake signups, prevents complaints, and improves list quality.
Why is repetitive or vague content risky?
Sending the same or similar emails triggers engagement drop-offs. Low engagement signals can cause mailbox providers to classify your emails as unwanted or spam.
Why should senders avoid attachments?
Attachments are often blocked at gateways for security reasons. This results in failed deliveries—and while not always a blocklist issue, the impact on deliverability is similar.
Why is including an unsubscribe link essential?
Hidden or missing opt-outs frustrate users, leading to spam complaints. These complaints directly damage sender reputation and trigger filtering.
How does sending frequency affect deliverability?
Infrequent sends lead to list decay, while over-sending overwhelms subscribers. A steady cadence keeps engagement healthy and reduces the likelihood of complaints.
Why does sender identity matter?
Emails sent from random or unmonitored addresses look suspicious to filters and users. Sending from a legitimate, monitored address builds trust and improves inbox placement.
What role does list hygiene play in avoiding blocks?
Removing invalid, bouncing, or disengaged recipients prevents unnecessary spam signals. Clean lists maintain strong sender reputation and reduce blocklist risk.
How can malware lead to blocklisting?
A compromised server can unknowingly send spam or phishing messages. Once detected, mailbox providers may block the server’s IP — harming all legitimate mail from that environment.
