What causes the bounce code 4.7.0 'Too many concurrent connections' and how can it be resolved?

Email marketer from MailPoet explains that shared SMTP servers often have connection limits, leading to 4.7.0 errors. Switching to a dedicated SMTP server or using a different port may alleviate this.

Marketer from Email Geeks shares that too many connections could be due to either the receiving mail server having a fixed limit or making decisions based on reputation. Only MailGun can change the connection limit, and it is a temporary failure so will likely eventually deliver.

Email marketer from dba.stackexchange details the importance of reviewing server settings to ensure you are within the receiving server's connection limits to prevent 4.7.0 errors.

Email marketer from Reddit explains that encountering 4.7.0 errors can be frustrating, but it often resolves itself after a short period, as it's a temporary issue. If it persists, it might indicate a problem with the sender's IP reputation or sending practices.

Email marketer from MXToolbox details the necessity of reviewing email headers and server logs can assist in diagnosing the root cause of 4.7.0 errors and identifying which server is imposing the connection limit.

Email marketer from Super User responds that 4.7.0 errors are commonly caused by exceeding connection limits or being rate-limited by the receiving server. This is a protective measure against spam and abuse.

Email marketer from SendPulse explains that to fix a 4.7.0 error, try reducing the number of emails you send at once, spacing out the emails over a longer period. Also, check your sending IP address isn't blacklisted, or has a good sender reputation.

Email marketer from Email on Acid shares that properly warming up new IPs and adhering to sending best practices helps avoid being flagged for sending too many concurrent connections, reducing the likelihood of 4.7.0 errors.

Email marketer from Email Marketing Guide explains that the bounce code 4.7.0 means 'Delivery temporarily deferred.' This typically means that the sending server has tried to deliver an email, but the receiving server is currently unavailable or too busy to accept it. It is usually a temporary issue, and the sending server will try again later.

Marketer from Email Geeks advises to contact Mailgun to make an adjustment, but to know that since it’s a shared pool it won’t consistently be an issue.

Marketer from Email Geeks states that moving to a dedicated IP will prevent resource/connection sharing and should resolve the issue.

Marketer from Email Geeks offers support to make adjustments and suggests creating a ticket to resolve the issues.

Email marketer from Stack Overflow mentions that a 4.7.0 error often indicates the sending server is attempting to make too many connections to the receiving server at once. This could be due to a high volume of emails being sent in a short period.

Expert from Word to the Wise explains that 4xx errors means that there was a temporary error when sending the message. The message was not accepted at that time, but may be accepted in the future. This is different than a 5xx error, where you'd need to modify the email before resending it.

Expert from Spam Resource explains that 4.7.0 errors are often due to throttling by the receiving mail server. This is a deliberate mechanism to limit the rate of incoming connections and messages from a particular sender or IP address to protect their infrastructure.

Expert from Email Geeks responds that the issue could be due to a poor-quality shared IP, however, it's likely on Mailgun to adjust the connection limits, particularly if it's a shared IP.

Expert from Email Geeks explains unless Mailgun gives a way to set up connection limits, this is on them to configure.

Documentation from Microsoft Learn explains that the 4.7.0 error typically indicates a temporary issue with the receiving server, such as being too busy to handle the connection. It can also arise from rate limiting or other anti-spam measures.

Documentation from Cisco.com details that concurrent connection limits are put in place to protect against denial of service or SPAM attacks. These limits can cause 4.7.0 errors if they are reached.

Documentation from Exim Wiki suggests 4.7.0 errors can stem from exceeding connection rate limits or the number of allowed simultaneous connections by the recipient server.

Documentation from Postfix.org explains managing the number of concurrent connections and adjusting settings related to connection rates can prevent 4.7.0 errors when using Postfix.