What causes connection limit issues with Optonline.net recipients?

Email marketer from Email Geeks suggests it sounds like a connection limit issue and asks if there is any idea how many simultaneous connections are being made to their servers.

Email marketer from Mailjet explains that ISPs use connection limits to protect their infrastructure from abuse. Sudden spikes in connection attempts from a single IP address can trigger these limits, resulting in temporary blocks or rate limiting.

Email marketer from Reddit suggests that Optonline, being a smaller ISP, might have more aggressive spam filtering and stricter connection limits compared to larger providers. This can lead to temporary blocks if your sending server exceeds their connection limits.

Email marketer from Email Geeks explains that the shared IP can matter and the number of connections allowed is often reduced for reputation issues. Two senders can have very different results even if their settings are identical.

Email marketer from SMTPGeek Forums explains shared IP reputation can impact connection limits, and Optonline may reduce connections allowed due to sender reputation, leading to different results for senders with identical settings.

Email marketer from Litmus answers shares that smaller ISPs like Optonline might have stricter and less transparent connection limits. Sending too many emails at once can result in temporary blocking. They advise warming up IP addresses carefully and gradually increasing sending volume.

Email marketer from Campaign Monitor explains that connection limits are implemented to prevent abuse of the mail server, helps to safeguard the server from potential overloading and DOS attacks. This is a security measure.

Email marketer from SendGrid shares that exceeding connection limits, especially with ISPs like Optonline, often results in temporary deferrals or rejections. They advise monitoring bounce codes and adjusting sending behavior accordingly to avoid these issues.

Email marketer from EmailGeeks Forum shares that Optonline is known to have strict connection limits and limited sender support. ESPs should avoid aggressive retries and set connection limits low to start.

Expert from Spam Resource explains that back in the dial-up era, residential ISPs like Optonline implemented strict connection limits to prevent users from running servers and hogging bandwidth. These limits often persist, causing issues for legitimate senders.

Expert from Word to the Wise shares that smaller ISPs like Optonline often have limited infrastructure and less sophisticated spam filtering systems. This can result in stricter and less transparent connection limits as a defensive measure.

Expert from Email Geeks explains that Optonline has some pretty strict limits and they’re utterly underfunded in the sender support department and suggests the ESP needs to back off, not aggressively retry and set connection limits low to start with.

Documentation from Message Systems' PowerMTA User Guide shares that connection throttling is a mechanism to control the number of concurrent connections to a specific domain. It is used to avoid overwhelming recipient servers and to comply with their connection limits, which helps in maintaining a good sender reputation.

Documentation from RFC Editor explains that SMTP servers can implement connection limits to manage server load and prevent abuse. Exceeding these limits can result in temporary rejections (421 errors) or permanent rejections (5xx errors).

Documentation from MXToolbox explains that a poor sender reputation can lead to recipient servers imposing stricter connection limits or blocking connections entirely. Maintaining a good sender reputation through proper authentication and responsible sending practices is crucial for avoiding connection issues.

Documentation from Google answers explains that bulk sender guidelines are in place to ensure emails are delivered to the inbox and not spam folders. They advise senders to monitor their sending reputation and avoid sending unsolicited emails. Google provides tools to track your domain's reputation. Maintaining a good sender reputation can help avoid connection limit issues.

Documentation from Microsoft answers explains that rate limiting policies are in place to ensure fair usage of their email services and prevent abuse. These limits can affect the number of connections, messages per connection, and message size. Exceeding these limits can result in temporary blocks or throttling.

Documentation from Amazon SES details that each Amazon SES account has a set of sending limits. These limits include the number of messages you can send per second and the number of messages you can send in a 24-hour period. Throttling is implemented as a safety measure to protect their customers' reputations and to maintain high deliverability rates. Exceeding your sending limits can result in temporary bounces or delivery delays.