What filtering methods do Optimum, Windstream, and CenturyLink use for email, and how can I troubleshoot content-related blocks?

Email marketer from Email Deliverability Blog shares that improving sender reputation is crucial to avoid blocks. She recommends authenticating your email with SPF, DKIM, and DMARC, and consistently sending valuable content to engaged subscribers.

Email marketer from Reddit r/emailmarketing shares that smaller ISPs like Optimum, Windstream, and CenturyLink often use a combination of Spamhaus, Spamcop, and internal blacklists. They recommend checking your IP against these blacklists first.

Email marketer from indiehackers.com says that another aspect to also consider is email warm up, especially on new IP addresses and new sending domains. ISP's use a metric called sending volume which can be a trigger for their spam filters. He recommends slowly increasing email sending volumes when starting.

Email marketer from Email Marketing Forum answers that content-related blocks often stem from trigger words or phrases that these ISPs flag as spam. He suggests using a spam checker tool to identify problematic content before sending.

Marketer from Email Geeks shares that if its content filtering he can assist by debugging using IPs and Subject lines.

Email marketer from quora.com answers that Optimum email blocks can be annoying if sending from different subnets as it can cause spam filters to kick in, this can be mitigated with correct SPF records to define the allowed subnets.

Email marketer from StackOverflow explains that if CenturyLink is your email provider and you are getting blocked it would be best to setup SPF and DKIM records. These records are used by receiving mail servers to ensure that a message really came from your domain and wasn't forged or spoofed.

Email marketer from cyberforum.ru suggests that content with attachments can cause issues if the attachments are executable files, he shares that some ISP's will instantly reject emails with executable file attachments.

Email marketer from dslreports.com forum mentions that Windstream primarily uses SpamAssassin with customized rules. He advises adjusting your content to lower the SpamAssassin score and testing email content using a spam checker.

Expert from Spam Resource explains that understanding SMTP error codes is important for troubleshooting email delivery issues. He highlights that 5xx errors are permanent failures and 4xx errors are temporary failures. The specific code helps pinpoint the reason for the block, such as content filtering or reputation issues.

Expert from Email Geeks explains that these ISPs mostly use home-grown filtering. She notes that Qwest and Centurylink are the same, and they bought part of Embarq, suggesting they might all be the same now.

Expert from Spam Resource shares that to troubleshoot content filtering, you need to analyze the message content and headers to identify triggers. She recommends using tools that simulate spam filters to test your messages before sending.

Expert from Word to the Wise explains that IP address reputation plays a crucial role in email deliverability. He mentions that a poor reputation can result in blocks, and it's essential to monitor your IP's reputation and take steps to improve it, such as following best practices and avoiding spam-like activities.

Expert from Word to the Wise explains managing your sender reputation is the key to email marketing success. He shares that the most impactful way to manage your sending reputation is to build your brand, be relevant, and be trustworthy.

Expert from Email Geeks responds that content is a significant factor in blocks. She suggests the issue could be the links or the fingerprint of the message. She also suggests that 'aggressive messaging' might indicate recipients don't want the mail, and something in the content identifies it as unwanted.

Documentation from DKIM.org details that DKIM (DomainKeys Identified Mail) is an email authentication method that uses a digital signature to verify the sender's identity. It helps prevent spoofing and improves deliverability.

Documentation from DMARC.org details that DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol that builds upon SPF and DKIM to provide a policy for handling emails that fail authentication checks. It allows domain owners to specify how recipient mail servers should handle unauthenticated messages.

Documentation from Spamhaus.org explains that Spamhaus uses a combination of IP and domain-based blacklists to identify and block spam sources. They detail the criteria for inclusion on their lists and the process for delisting.

Documentation from CenturyLink answers that CenturyLink's Acceptable Use Policy outlines prohibited email practices, including spamming, phishing, and the transmission of malicious content. Violations can result in account suspension or termination.