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SMTP Email Error 504 - How to Resolve [SOLVED]

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    As the standard protocol at the core of email communication, Simple Mail Transfer Protocol (SMTP) is essential to the way emails are delivered and received over the Internet. This protocol is essential for commercial and personal communications as it guarantees that your emails go to their intended recipients quickly. On the other hand, SMTP problems, like Error 504, might seriously impede this operation.

    Email communication can be significantly impacted by SMTP Error 504, which frequently arises from server timeouts and delays or stops email transmission entirely. Communication problems, missing deadlines, and lost business opportunities may result from this. The error signals a more complicated problem with the network or server settings that needs to be fixed right away in order to get functionality back.

    Interpreting SMTP error 504

    When an SMTP server is unable to finish a request within the allotted time limit, it results in SMTP Email Error 504. This error is commonly represented by a “504 Gateway Timeout” message. This error indicates a serious breakdown in communication between the servers involved in the email transmission process, not just a small annoyance.

    How Does the SMTP Email Error 504 Appear?

    Depending on the email client or server system, the error can frequently appear in multiple ways:

    1. The most frequent symptom, “504 Gateway Timeout,” indicates that the server takes too long to send a request or answer.
    2. “504 Timeout Waiting for External Server”. This version denotes that the SMTP server was unable to get a timely answer from another server it was corresponding with, which could have been a communication intermediary such as a routing or authentication server.

    Causes of SMTP error 504 in emails

    Server Timeout Issues

    The root cause of a 504 error is usually that the SMTP server failed to respond to a request from another server or client within the minimum turnaround time. This occurs when the server is under high traffic conditions, overwhelmed, or lacks the necessary resources like CPU and memory to meet the requirements.

    Network Problems

    Connectivity issues within the network can also lead to 504. These problems may include network congestion, slow or unstable network connections, or faulty networking hardware that intermittently disrupts communication between servers. Therefore, such issues can delay the server responses beyond the acceptable timeout threshold.

    Server Unavailability

    Sometimes, the server to process the email request might be temporarily be unavailable, either due to maintenance, updates, or sudden shutdown. It could also be that the primary server relies on response from these unavailable systems and fail to get responds; the authentication servers, the database servers, among others. Hence the cause of a 504 error.

    Configuration Errors

    Timeouts may also result from incorrect network equipment or SMTP server settings. This includes badly configured firewalls, routers, or server settings that lead to inappropriate connection handling or incorrectly limit the amount of time a server may react to email queries.

    External Dependencies

    SMTP servers frequently rely on outside systems to provide tasks like virus screening, spam detection, and authentication. The entire email sending process may be delayed by these unresponsive or slow systems, which could lead to an SMTP server timeout and a 504 error.

    Detailed solutions for resolving SMTP error 504 in popular email clients


    1. Check Network Connection. Ensure your internet connection is stable and fast enough to handle SMTP communications without timeouts.
    2. Modify Server Timeout Settings. Gmail users typically don’t have direct access to modify SMTP timeout settings as these are managed by Google. However, if you’re using a third-party app with Gmail, check the application’s settings to adjust the server timeout.
    3. Contact Support. If problems persist, contacting Google support or consulting their help forums may provide solutions specifically tailored to Gmail-related SMTP issues.


    1. Adjust Server Timeouts.
      • Open Outlook and go to File > Info > Account Settings > Account Settings.
      • Select your email account and click Change.
      • Click More Settings and navigate to the Advanced tab.
      • Increase the server timeout slider to a higher value to allow more time for server responses.
    2. Test Email Server Availability. Use the “Test Account Settings” feature by clicking on it after adjusting the timeouts to verify connectivity to the mail server.


    1. Ensure Server Connectivity:
      • Log into your Yahoo Mail account.
      • Go to Settings > More Settings > Mailboxes.
      • Select your account and scroll down to Outgoing Mail Server (SMTP).
      • Make sure the server settings are correct (smtp.mail.yahoo.com), and the port is set appropriately (usually 465 for SSL or 587 for STARTTLS).
    2. Adjust Timeout Settings. Similar to Gmail, Yahoo users generally cannot adjust SMTP timeout settings directly through the web interface. Use any third-party email clients configured with Yahoo Mail to modify these settings if available.

    Other email clients

    1. Verify SMTP Settings. Ensure that the SMTP settings (server address, port, encryption) are correctly configured according to your email provider’s recommendations.
    2. Increase Timeout Settings:
      • Access the account settings or preferences menu.
      • Find the section related to server or network settings and adjust the timeout settings to give more time for connections.
    3. Check External Dependencies. Make sure any external systems (like antivirus or firewall settings) are not blocking or slowing down your SMTP communications.
    4. Test the Connection. Most email clients offer a way to test the server settings. Use this feature to verify that the client can successfully connect to the SMTP server.

    Explaining variations of SMTP error 504

    There are various ways that SMTP Error 504 can appear, and each one indicates a different problem with the SMTP communication process. Two popular versions, 504 5.7.4 and 504 5.5.2, are explained as follows:

    504 5.7.4: Problems with Authentication Timing

    Authentication procedure time difficulties are frequently indicated by the error code 504 5.7.4. This error may arise because the authentication process is excessively complicated and time-consuming, or because the SMTP server takes too long to authenticate a command because of delays in accessing authentication servers or databases. This error number appears when the server finally times out. Assuring that authentication requests are handled effectively and within reasonable time constraints usually entails assessing and optimizing the authentication infrastructure in order to resolve this problem.

    504 5.5.2: Inaccurate Order in the Command Sequence

    In contrast, 504 5.5.2 indicates that there may have been a miscommunication or a timing error in the directives that were transmitted during the SMTP operation. This could result from commands that are not processed in the correct order or from a delay in processing commands that makes the server time out before the sequence of commands is finished. It’s crucial to make sure that all SMTP commands are sent in the right order and that they are processed quickly in order to resolve this particular Error 504.

    Benefits of using email warm-up services

    In this regard, specialists recommend using email warm-up services, such as Warmy.io, which not only effectively prevents SMTP errors but also reliably protects the sender’s reputation. Warmy.io gradually increases the number of emails sent from a new or reactivated email address, thus raising credibility with Internet Service Providers and reducing the risk of emails being labeled as spam.

    Moreover, the Warmy.io platform offers a wide range of critical functions, which further ensures email safety and reliability. It allows users to perform an email deliverability test for free and evaluate the chances of their emails reaching the user’s inbox instead of being blocked by spam filters.

    Furthermore, this tool conducts blacklist checks and assures that users’ addresses are not included in any of the lists since it can have a detrimental effect on email output.

    Lastly, with its option for generating SPF and DMARC records that are critical for enhancing secure email authentication and increasing the chances of acceptance by recipient servers, Warmy.io becomes an indispensable tool for flawless and immediate email communication.


    It is essential to fix SMTP Email Error 504 as early as possible to avoid email service interruptions and ensure timely reception of crucial messages. This error, commonly associated with server timeouts or server misbehaviors, can significantly disrupt private and corporate confirmed as well as automated email correspondences.

    Users who understand and fix the root sources of the SMTP Email Error 504 can prevent severe communication outages that may cause various processes and relationships to fail. Additionally, users should embrace proactive email systems management to make sure occurrences such as this one do not happen. This can be achieved by hiring the Warmy.io professionals to warm up their inboxes. Warmy.io also offers deliverability tests, blacklist checks, and SPF and DMARC records.


    SMTP Email Error 504: What Is It?

    SMTP Email Error 504, also known as "504 Gateway Timeout," happens when an SMTP server is unable to fulfill a request in the allotted amount of time. This is frequently the result of network or server overload.

    The reason behind SMTP Email Error 504?

    Numerous things, such as server timeouts, poor network connectivity, unavailable servers, incorrect configuration, or reliance on sluggish or unresponsive external services, can result in this error.

    How can I resolve Gmail's SMTP Email Error 504?

    Although Gmail users are unable to directly modify SMTP timeout settings, they can address underlying issues causing Error 504 by making sure they have a steady internet connection and contacting Google support.

    What should I do in the event that Outlook displays SMTP Error 504?

    To change the server timeout settings in Outlook, go to Account Settings, choose your email account, and make the necessary changes under the 'More Settings' and 'Advanced' tabs.

    How can I avoid the 504 SMTP Email Error?

    Maintaining an updated server and software, configuring your email systems correctly, monitoring and improving your email system using tools like Warmy.io, and making sure your network connection is dependable are all necessary to prevent SMTP Error 504.

    Does using an email warm-up service like Warmy.io help with SMTP Error 504?

    Indeed, employing an email warm-up service such as Warmy.io contributes to the preservation of a positive sender reputation and guarantees that emails are not returned or tagged as spam, all of which can help avert problems such as SMTP Error 504.

    Are there any tools to check if my email settings might contribute to SMTP Error 504?

    Indeed, programs like Warmy.io offer features like email deliverability testing and the creation of SPF/DKIM/DMARC records that can assist make sure your email settings are optimized and lower the chance of running into SMTP issues

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