{"id":7938,"date":"2025-01-14T13:05:42","date_gmt":"2025-01-14T10:05:42","guid":{"rendered":"https:\/\/snov.io\/knowledgebase\/?p=7938"},"modified":"2025-02-23T18:23:03","modified_gmt":"2025-02-23T15:23:03","slug":"common-smtp-errors-and-how-to-solve-them","status":"publish","type":"post","link":"https:\/\/snov.io\/knowledgebase\/common-smtp-errors-and-how-to-solve-them\/","title":{"rendered":"How to fix common email SMTP connection errors"},"content":{"rendered":"<p><span style=\"font-weight: 400;\">In this article, you\u2019ll learn about email connection errors, their possible reasons, common error examples, and how to fix them.\u00a0<\/span><\/p>\n<p><a href=\"#when-connection-errors-happen\">When connection errors happen<\/a><\/p>\n<p><a href=\"#common-error-reasons\">Common error reasons<\/a><\/p>\n<p><a href=\"#examples-smtp-errors\">Real SMTP error examples<\/a><\/p>\n<p><a href=\"#how-to-troubleshoot-errors\">How to read and troubleshoot errors<\/a><\/p>\n<p><span style=\"font-weight: 400;\">In some cases when you add your email accounts to Snov.io, you may receive an error indicating that the connection failed.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">You might think, \u201cWhy is this happening? I entered everything correctly \u2014 it must be a Snov.io issue.\u201d To eliminate any confusion around this issue, we\u2019ll explain why these errors happen and how you can fix them.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-36534 wp-block-image shadow\" src=\"https:\/\/snov.io\/knowledgebase\/wp-content\/uploads\/2025\/01\/email-error.png\" alt=\"\" width=\"1600\" height=\"759\" srcset=\"https:\/\/snov.io\/knowledgebase\/wp-content\/uploads\/2025\/01\/email-error.png 1600w, https:\/\/snov.io\/knowledgebase\/wp-content\/uploads\/2025\/01\/email-error-300x142.png 300w, https:\/\/snov.io\/knowledgebase\/wp-content\/uploads\/2025\/01\/email-error-1024x486.png 1024w, https:\/\/snov.io\/knowledgebase\/wp-content\/uploads\/2025\/01\/email-error-768x364.png 768w, https:\/\/snov.io\/knowledgebase\/wp-content\/uploads\/2025\/01\/email-error-1536x729.png 1536w\" sizes=\"(max-width: 1600px) 100vw, 1600px\" \/><\/p>\n<h2 id=\"when-connection-errors-happen\"><strong>When connection errors happen<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Snov.io uses the settings you provide to establish a secure connection. This includes connecting to your provider\u2019s servers via SMTP and IMAP and accessing your email account with your credentials (username and password).<\/span><\/p>\n<div class=\"notification-block learn\">\n<div class=\"notification-block__icon\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/snov.io\/knowledgebase\/wp-content\/themes\/knowledgebase-n\/assets\/img\/fluent_chat-warning-16-regular.svg\" alt=\"learn\" width=\"32\" height=\"32\" \/><\/div>\n<div class=\"notification-block__text\">\n<p>Your provider responds with either a \u201csuccess\u201d or \u201cfailure.\u201d If the connection is unsuccessful, their response includes an error message. This message appears in the notification on your Snov.io interface.<\/p>\n<\/div>\n<\/div>\n<p><span style=\"font-weight: 400;\">Since the error message originates directly from your email provider and often includes important details about the issue, Snov.io displays it exactly as received. This ensures you have the first source information to use for troubleshooting.<\/span><\/p>\n<h2 id=\"common-error-reasons\"><strong>Common error reasons<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Let\u2019s review possible reasons for email connection issues and how to fix them.<\/span><\/p>\n<ul>\n<li aria-level=\"1\"><b>The connection failed due to incorrect email account credentials<\/b><\/li>\n<\/ul>\n<p><b>Possible reasons:<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Such errors happen when the email credentials you entered (username and password) are incorrect or have mistakes.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In the error message, it could be determined as <\/span><i><span style=\"font-weight: 400;\">\"Authentication failed\"<\/span><\/i><span style=\"font-weight: 400;\"> or <\/span><i><span style=\"font-weight: 400;\">\"Username\/password not accepted.\"<\/span><\/i><\/p>\n<p><b>Solution:<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Double-check the details in the <\/span><b>Username<\/b><span style=\"font-weight: 400;\"> and <\/span><b>Password<\/b><span style=\"font-weight: 400;\"> fields. This issue can happen even if you enter the correct password. Some email providers (Gmail) block connections when you use your real password in other apps.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">To resolve it, you may need to create a special password. It\u2019s usually called an \u201capp password\u201d or \u201capp-specific password\u201d \u2013 you can create it in account security settings with the provider. <\/span><a href=\"https:\/\/snov.io\/knowledgebase\/how-to-create-and-use-gmail-app-password\/\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Read how to create it in Gmail.<\/span><\/a><span style=\"font-weight: 400;\"> Then, enter it in the email settings in Snov.io.<\/span><\/p>\n<ul>\n<li aria-level=\"1\"><b>The connection to the provider's server failed due to incorrect SMTP settings<\/b><\/li>\n<\/ul>\n<p><b>Possible reasons:<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Such errors occur when any of the SMTP parameters are entered incorrectly, such as the SMTP host, SMTP port, or encryption type (SSL or TLS).<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In the error message, this issue could be determined as<\/span><i><span style=\"font-weight: 400;\"> \u201cConnection could not be established with host \u201cyour SMTP host\u201d. \u201cName or service not known\u201d or \u201cTemporary failure in name resolution\u201d.<\/span><\/i><\/p>\n<p><b>Solution:<\/b><\/p>\n<p><span style=\"font-weight: 400;\">To avoid such errors, check your SMTP settings for any typos or format errors. Confirm that the SMTP host and port are correct according to your provider\u2019s specifications. Double-check with the official documentation for connecting to other services via SMTP\/IMAP.<\/span><\/p>\n<ul>\n<li aria-level=\"1\"><b>The connection failed due to temporary technical issues on the provider\u2019s side<\/b><\/li>\n<\/ul>\n<p><b>Possible reasons:<\/b><\/p>\n<p><span style=\"font-weight: 400;\">During an email connection, the provider\u2019s server is expected to respond within a specific time limit (in seconds). If the server doesn't respond in time, you may encounter errors. In the error message, it could be described as <\/span><i><span style=\"font-weight: 400;\">\u201cConnection to host timed out.\u201d<\/span><\/i><\/p>\n<p><span style=\"font-weight: 400;\">Poor connectivity can cause issues in real campaigns, so we\u2019ve set a \u201cresponse time\u201d threshold to prevent such issues.<\/span><\/p>\n<p><b>Solution:<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Check the connection again after some time. If there\u2019s still no success, it means that the SMTP host you use has unstable connectivity. For a stable connection, consider switching to a different provider. We recommend Gmail (Google Workspace) as one of the most reliable providers.<\/span><\/p>\n<ul>\n<li aria-level=\"1\"><b>The connection failed because your provider\u2019s server blocks connection from \u201cunknown\u201d parties<\/b><\/li>\n<\/ul>\n<p><b>Possible reasons:<\/b><\/p>\n<p><span style=\"font-weight: 400;\">This type of error usually happens because your email provider has rejected connection requests from Snov.io. We connect to your provider using specific IP addresses. If these IPs aren't permitted, the connection will fail. In the error message, this issue could be described as: <\/span><i><span style=\"font-weight: 400;\">\u201cSocket timeout\u201d, \u201cConnection could not be established with SMTP host\u201d, \u201cConnection timeout\u201d<\/span><\/i><span style=\"font-weight: 400;\">.<\/span><\/p>\n<p><b>Solution:<\/b><\/p>\n<p><span style=\"font-weight: 400;\">To resolve this error, you may need to whitelist Snov.io IP addresses:<\/span><\/p>\n<p><b>For SMTP: <\/b><span style=\"font-weight: 400;\">Add our SMTP IP addresses to your provider\u2019s whitelist or your custom email server\u2019s whitelist.<\/span><\/p>\n<p><b>For IMAP: <\/b><span style=\"font-weight: 400;\">If SMTP connections are successful but IMAP connections fail, add our IMAP IP addresses to the whitelist as well.<\/span><\/p>\n<div class=\"notification-block learn\">\n<div class=\"notification-block__icon\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/snov.io\/knowledgebase\/wp-content\/themes\/knowledgebase-n\/assets\/img\/fluent_chat-warning-16-regular.svg\" alt=\"learn\" width=\"32\" height=\"32\" \/><\/div>\n<div class=\"notification-block__text\">\n<p><strong>Contact support:<\/strong> To get further assistance on how to whitelist our IP addresses, please reach out to our support team. They can provide detailed instructions and the specific IP addresses required.<\/p>\n<\/div>\n<\/div>\n<h2 id=\"examples-smtp-errors\"><strong>Real examples of SMTP errors<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Below, we\u2019ll provide examples of real connection errors we\u2019ve among accounts Snov.io users connect. <\/span><\/p>\n<div class=\"notification-block note-gray\">\n<div class=\"notification-block__text\">\n<p>To find your error here, copy the error message from your interface and search it on this page. To search through the content, use combination \u201cCmd + F\u201d on Mac, or \u201cCtrl + F\u201d on Windows.<\/p>\n<\/div>\n<\/div>\n<p><b>1) 535-5.7.8 Username and Password not accepted.<\/b><\/p>\n<p><span style=\"font-weight: 400;\">This error happens when the email address entered in the <\/span><b>Username<\/b><span style=\"font-weight: 400;\"> field and\/or the password is incorrect or doesn\u2019t match with the username (the password belongs to a different account).<\/span><\/p>\n<p><span style=\"font-weight: 400;\">If the password is correct, the error could happen because Gmail requires you to use the \u201capp password\u201d instead of the real password. Enter the <\/span><a href=\"https:\/\/snov.io\/knowledgebase\/how-to-create-and-use-gmail-app-password\/\"><span style=\"font-weight: 400;\">app password created in your Gmail account<\/span><\/a><span style=\"font-weight: 400;\">, not your actual password for logging in to Gmail.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The app password also should be for the appropriate Gmail user (email address). Each Gmail user within a Workspace account must have their unique app password.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">If you\u2019re connecting multiple accounts from the same domain or organization, make sure you use an app password created specifically for each account.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">If you still don\u2019t get a \u201cSuccess\u201d status, try creating a new app password, as the one you\u2019re using may have expired.<\/span><\/p>\n<p><b>2) Connection could not be established with host \"ssl:\/\/smtp.gmail.com:465\": stream_socket_client(): Unable to connect to ssl:\/\/smtp.gmail.com:465 (Network is unreachable).<\/b><\/p>\n<p><span style=\"font-weight: 400;\">This error indicates that the host <\/span><a href=\"http:\/\/smtp.gmail.com\"><span style=\"font-weight: 400;\">smtp.gmail.com<\/span><\/a><span style=\"font-weight: 400;\"> (Gmail\u2019s host) could not be reached through port 465 at the time the error occurred. As a result, Snov.io was unable to establish a connection.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">This may be due to temporary issues with Google\u2019s email server or because you\u2019re using Gmail\u2019s host with an email server hosted on another platform (such as Amazon Web Services).<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In some cases, the issue arises because your email server blocks requests to Gmail\u2019s port 465. To resolve this, you may need to update the server\u2019s security policy to allow connection requests to Gmail\u2019s ports.<\/span><\/p>\n<p><b>3) Connection to \"smtp.office365.com:587\" timed out; Connection to \"smtppro.zoho.com:587\" timed out.<\/b><\/p>\n<p>This error indicates that the connection to the host (your provider\u2019s server) was interrupted or couldn\u2019t be established because a \u201csuccess\u201d response wasn\u2019t received within the expected time frame.<\/p>\n<p>To address this issue, retry the connection later: Use the <strong>Check connection<\/strong> option in your email settings after waiting for a while. If the connection still fails, it may mean that your provider is experiencing unstable connectivity at the moment. This issue is likely temporary.<\/p>\n<p><b>4) Expected response code \"250\" but got code \"452\", with message \"IP **** temporarily rejected for too many messages sent. Please check any clients or devices that may be misconfigured, and try again later.<\/b><\/p>\n<p>This error can happen because your provider may have greylisted the IP address you're sending from because too many emails are being sent in a short period. This doesn't necessarily mean the emails are all from you. The provider\u2019s email server might be temporarily overloaded.<\/p>\n<p><span style=\"font-weight: 400;\">Errors with code \u201c4..\u201d mean they are temporary and will likely resolve without your interference. <\/span>In most cases, simply wait a while and check the connection from account settings. If the problem persists, reach out to your email provider for assistance.<\/p>\n<p><span style=\"font-weight: 400;\">You may also check if your sender IP addresses have been blacklisted. You can check this in your <\/span><a href=\"https:\/\/app.snov.io\/deliverability\/#\/check\/first-visit\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">deliverability test<\/span><\/a><span style=\"font-weight: 400;\"> results.<\/span><\/p>\n<p><b>5) Expected response code \"250\" but got code \"550\", with message \"550 5.7.1 Sender daily limit exceeded\".<\/b><\/p>\n<p><span style=\"font-weight: 400;\">This error indicates that you might have reached your email sending limit, and your provider has temporarily restricted your account. If you think this is a mistake, please reach out to your provider to check the details of your account.<\/span><\/p>\n<p><b>6) Connection could not be established with host \u201cyour SMTP host\u201d stream_socket_client(): Unable to connect to \u201cyour SMTP host\u201d (Connection refused).<\/b><\/p>\n<p><span style=\"font-weight: 400;\">This error means that your provider\u2019s email server or the custom email server you use doesn\u2019t accept connection requests from Snov.io. Look for any parameters in your server\u2019s settings or any policies that might be causing this error.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">To resolve this issue, you may need to whitelist Snov.io in your email server settings. Contact our support team for more information on how to proceed.<\/span><\/p>\n<p><b>7) Connection could not be established with host \"your SMTP host\": stream_socket_client(): SSL operation failed with code 1. OpenSSL Error messages:errorSSL routines:tls_process_server_certificate:certificate verify failed.<\/b><\/p>\n<p><span style=\"font-weight: 400;\">This error indicates that the SSL certificate on your email server has likely expired or is invalid, and it needs to be renewed or updated. To fix this issue, ensure that the SSL certificate is properly configured and recognized. Consult with your email server administrator to get a solution.<\/span><\/p>\n<p><b>8) Expected response code \"250\" but got code \"501\", with message \"501 tenant external recipient exceeds quota.<\/b><\/p>\n<p><span style=\"font-weight: 400;\">This error usually indicates an issue on the recipient's end rather than your email settings. It\u2019s likely reason is that the recipient's mailbox has reached or exceeded its storage capacity, preventing new emails from being delivered.<\/span><\/p>\n<h2 id=\"how-to-troubleshoot-errors\"><strong>How to read and troubleshoot errors<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">If you haven\u2019t found your error in the list of examples, give it a shot at troubleshooting it yourself.<\/span><\/p>\n<p>While the error message might seem confusing, it can contain useful information. It usually includes an SMTP error code and a message explaining the issue as determined by your provider. Use these details to:<\/p>\n<div class=\"notification-block learn\">\n<div class=\"notification-block__icon\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/snov.io\/knowledgebase\/wp-content\/themes\/knowledgebase-n\/assets\/img\/fluent_chat-warning-16-regular.svg\" alt=\"learn\" width=\"32\" height=\"32\" \/><\/div>\n<div class=\"notification-block__text\">\n<p><strong>Search online:<\/strong> Look up the specific error code you got to find solutions on the internet.<\/p>\n<p><strong>Contact provider's support:<\/strong> If you cannot resolve the issue on your own, submit a support ticket to your email provider with the error information.<\/p>\n<\/div>\n<\/div>\n<p><span style=\"font-weight: 400;\">Let\u2019s break down these examples:<\/span><\/p>\n<p><b>1) Expected response code \"250\" but got code \"550\", with message \"550 5.7.1 Sender daily limit exceeded \".<\/b><\/p>\n<p><span style=\"font-weight: 400;\">It means that the provider\u2019s server was expected to respond with SMTP code 250 (success), but instead, it responded with code 550. The following message explains the reason for the error\u2014in this case, the account\u2019s daily sending limit has been exceeded.<\/span><\/p>\n<p><strong>2) Expected response code 250\/251\/252 but got code 451, with message 451 Temporary local problem - please try later. errNo=245178<\/strong><\/p>\n<p>Similar to the previous example, this error indicates that the provider responded with SMTP code \"451.\" The message explains that there was a temporary issue on the provider's side during the connection attempt and recommends trying to connect again later.<\/p>\n<div class=\"notification-block learn\">\n<div class=\"notification-block__icon\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/snov.io\/knowledgebase\/wp-content\/themes\/knowledgebase-n\/assets\/img\/fluent_chat-warning-16-regular.svg\" alt=\"learn\" width=\"32\" height=\"32\" \/><\/div>\n<div class=\"notification-block__text\">\n<p>Couldn\u2019t find the solution to your error? Message our support team for help - we\u2019ll provide any assistance we can.<\/p>\n<\/div>\n<\/div>\n<h2><strong>Alternative outreach channel<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">When there are temporary issues with your email accounts, you can use LinkedIn Automation as an additional way to contact your prospects.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In your account, add slots and <\/span><a href=\"https:\/\/snov.io\/knowledgebase\/how-to-connect-your-linkedin-account-to-snov-io\/\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">connect LinkedIn accounts<\/span><\/a><span style=\"font-weight: 400;\"> to enable the LinkedIn add-on. It lets you create LinkedIn sequences to automatically visit prospects\u2019 profiles, send connection requests, messages, and InMails. <\/span><a href=\"https:\/\/snov.io\/knowledgebase\/how-to-use-snov-io-linkedin-automation\/\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Learn how to set up a LinkedIn campaign.<\/span><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>In this article, you\u2019ll learn about email connection errors, their possible reasons, common error examples, and how to fix them.\u00a0 When connection errors happen Common error reasons Real SMTP error examples How to read and troubleshoot errors In some cases when you add your email accounts to Snov.io, you may receive an error indicating that [&hellip;]<\/p>\n","protected":false},"author":16,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1962],"tags":[],"_links":{"self":[{"href":"https:\/\/snov.io\/knowledgebase\/wp-json\/wp\/v2\/posts\/7938"}],"collection":[{"href":"https:\/\/snov.io\/knowledgebase\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/snov.io\/knowledgebase\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/snov.io\/knowledgebase\/wp-json\/wp\/v2\/users\/16"}],"replies":[{"embeddable":true,"href":"https:\/\/snov.io\/knowledgebase\/wp-json\/wp\/v2\/comments?post=7938"}],"version-history":[{"count":1,"href":"https:\/\/snov.io\/knowledgebase\/wp-json\/wp\/v2\/posts\/7938\/revisions"}],"predecessor-version":[{"id":37436,"href":"https:\/\/snov.io\/knowledgebase\/wp-json\/wp\/v2\/posts\/7938\/revisions\/37436"}],"wp:attachment":[{"href":"https:\/\/snov.io\/knowledgebase\/wp-json\/wp\/v2\/media?parent=7938"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/snov.io\/knowledgebase\/wp-json\/wp\/v2\/categories?post=7938"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/snov.io\/knowledgebase\/wp-json\/wp\/v2\/tags?post=7938"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}