Why are Optonline.net emails bouncing but sometimes still delivering?
Summary
What email marketers say9Marketer opinions
Email marketer from GlockApps suggests using a seed list to test email deliverability across different ISPs, including Optonline. This can help identify if emails are being filtered or bounced, and provide insights into the potential causes.
Email marketer from Twilio SendGrid discusses that the content of the emails might trigger spam filters at Optonline, especially if it contains certain keywords or phrases commonly associated with spam. This can cause some emails to be delivered while others are blocked.
Email marketer from StackOverflow suggests that Optonline could be using a greylisting technique or implementing temporary blocks due to suspected spam activity. This could explain the intermittent delivery and bounces.
Email marketer from Litmus blog recommends verifying that email authentication (SPF, DKIM, DMARC) is properly configured. Incorrect authentication settings can cause ISPs like Optonline to flag emails as suspicious, leading to inconsistent delivery.
Email marketer from EmailMarketingTips.com shares that intermittent bounces often indicate reputation-based filtering. Optonline may be throttling or rejecting emails from senders with low reputation scores, resulting in some emails getting through while others are blocked.
Email marketer from Email Geeks Forum mentions list hygiene as a factor. If the email list contains a high percentage of inactive or invalid email addresses, Optonline may flag the sender as a spammer, causing inconsistent delivery.
Email marketer from Mailchimp suggests checking if the sending IP address or domain is on any blocklists. Being listed on a blocklist can cause delivery issues with certain ISPs, including Optonline, resulting in sporadic bounces.
Email marketer from Reddit suggests that Optonline, like many ISPs, might have inconsistent filtering rules, leading to some emails being delivered while others bounce. They also mention that reputation and content play a role.
Email marketer from Email on Acid discusses that rendering issues within the emails might be triggering spam filters leading to inconsistent delivery.
What the experts say3Expert opinions
Expert from Email Geeks shares that they are seeing bounce issues across a number of accounts, but also seeing successful delivery at the same time to Optonline.net.
Expert from Spam Resource explains that ISPs like Optonline might use variable filtering techniques based on numerous factors (sender reputation, content, user engagement) leading to some emails being delivered while others bounce. They advise monitoring bounce codes and adjusting sending practices accordingly.
Expert from Word to the Wise discusses that if Optonline.net is a significant portion of your email sending, they recommend ensuring you are signed up for the feedback loops. These can provide insight as to why Optonline are flagging your emails as spam.
What the documentation says5Technical articles
Documentation from DMARC.org outlines that DMARC policies (none, quarantine, reject) instruct receiving mail servers on how to handle emails that fail authentication checks. If a sender's DMARC policy is not properly configured, Optonline might handle those emails inconsistently.
Documentation from Google Postmaster Tools states the necessity to monitor spam rates, maintain low complaint rates, and authenticate emails properly using SPF, DKIM, and DMARC. Failing to meet these requirements can lead to delivery issues with ISPs like Optonline.
Documentation from RFC Editor explains that SMTP servers return error codes for different bounce reasons. A 5xx error indicates a permanent failure (email will not be delivered), while a 4xx error suggests a temporary issue (delivery may be retried). Optonline could be using either, depending on the specific filtering rules.
Documentation from Validity emphasizes the importance of sender reputation. ISPs like Optonline often use reputation scores to determine whether to accept, reject, or filter incoming emails. Low or inconsistent sender reputation can lead to unpredictable delivery patterns.
Documentation from Microsoft explains that SPF records are used to prevent spammers from sending messages with forged "from" addresses at your domain. If SPF records are not correctly configured then it could lead to Optonline sometimes blocking messages.