{"id":821,"date":"2025-12-19T09:53:59","date_gmt":"2025-12-19T08:53:59","guid":{"rendered":"https:\/\/mybox.com\/help\/?post_type=manual_kb&#038;p=821"},"modified":"2026-05-30T16:52:55","modified_gmt":"2026-05-30T14:52:55","slug":"protocols-smtp","status":"publish","type":"manual_kb","link":"https:\/\/mybox.com\/help\/en\/knowledgebase\/protocols-smtp\/","title":{"rendered":"Protocols &#8211; SMTP"},"content":{"rendered":"\n<div class=\"translation-block translation-block-merged\">\n<p class=\"wp-block-paragraph\">SMTP (Simple Mail Transfer Protocol) is a network protocol used for sending email messages between servers. It defines how emails are transmitted from a sender to a mail server and between mail servers across the internet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">SMTP is the standard protocol responsible for outgoing email delivery in most email systems.<\/p>\n\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_86 ez-toc-wrap-left counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/mybox.com\/help\/en\/knowledgebase\/protocols-smtp\/#How_SMTP_works\" >How SMTP works<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/mybox.com\/help\/en\/knowledgebase\/protocols-smtp\/#SMTP_communication_process\" >SMTP communication process<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/mybox.com\/help\/en\/knowledgebase\/protocols-smtp\/#Ports_used_by_SMTP\" >Ports used by SMTP<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/mybox.com\/help\/en\/knowledgebase\/protocols-smtp\/#SMTP_and_email_retrieval\" >SMTP and email retrieval<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/mybox.com\/help\/en\/knowledgebase\/protocols-smtp\/#Security_considerations\" >Security considerations<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/mybox.com\/help\/en\/knowledgebase\/protocols-smtp\/#Practical_use_cases\" >Practical use cases<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/mybox.com\/help\/en\/knowledgebase\/protocols-smtp\/#Practical_implications\" >Practical implications<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/mybox.com\/help\/en\/knowledgebase\/protocols-smtp\/#Summary\" >Summary<\/a><\/li><\/ul><\/nav><\/div>\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"How_SMTP_works\"><\/span>How SMTP works<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<\/div>\n\n<div id=\"mybox-2253139485\" class=\"mybox-content mybox-entity-placement\"><div class=\"early-access-banner-inpost\">\r\n  <div class=\"banner-left-inpost\">\r\n    <div class=\"icon-box-inpost\">\r\n      <img decoding=\"async\" src=\"https:\/\/mybox.com\/help\/wp-content\/uploads\/2026\/02\/square-info-icon.svg\" alt=\"Info\">\r\n    <\/div>\r\n    <div class=\"text-box-inpost\">\r\n      <span class=\"label-inpost\"><span class=\"translation-block translation-block-banner-text\">Early access<\/span><\/span>\r\n      <h4><span class=\"translation-block translation-block-banner-text\">Still need help?<\/span><\/h4>\r\n      <p><span class=\"translation-block translation-block-banner-text\">Contact our customer service team.<\/span><\/p>\r\n    <\/div>\r\n  <\/div>\r\n\r\n  <div class=\"banner-right-inpost\">\r\n    <a href=\"https:\/\/panel.mybox.com\/helpdesk2\/v\/list\/\" class=\"banner-button-inpost\"><span class=\"translation-block translation-block-banner-text\">Message us<\/span><\/a>\r\n  <\/div>\r\n<\/div><\/div>\n\n<div class=\"translation-block translation-block-merged\"><p class=\"wp-block-paragraph\">SMTP operates using a client\u2013server model.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">When an email is sent:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the email client connects to an outgoing mail server<\/li>\n\n\n\n<li>the server processes the message and identifies the recipient domain<\/li>\n\n\n\n<li>the message is forwarded to the recipient\u2019s mail server<\/li>\n\n\n\n<li>the recipient server stores the message for later retrieval<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">SMTP is only responsible for sending and relaying email. Receiving email is handled by other protocols such as IMAP or POP3.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"SMTP_communication_process\"><\/span>SMTP communication process<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">An SMTP session follows a structured sequence of commands between systems:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>connection is established over TCP<\/li>\n\n\n\n<li>the sending server identifies itself<\/li>\n\n\n\n<li>sender and recipient addresses are specified<\/li>\n\n\n\n<li>message content is transmitted<\/li>\n\n\n\n<li>the session is closed after delivery<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This process ensures standardized communication between different mail systems.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Ports_used_by_SMTP\"><\/span>Ports used by SMTP<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">SMTP typically uses the following ports:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Port 25<\/strong> \u2013 server-to-server email transfer<\/li>\n\n\n\n<li><strong>Port 587<\/strong> \u2013 email submission from clients (recommended with authentication)<\/li>\n\n\n\n<li><strong>Port 465<\/strong> \u2013 secure SMTP using SSL\/TLS (legacy but still supported in some systems)<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"SMTP_and_email_retrieval\"><\/span>SMTP and email retrieval<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">SMTP is used only for sending emails.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">To receive and read emails, different protocols are used:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>IMAP \u2013 synchronizes emails with the server<\/li>\n\n\n\n<li>POP3 \u2013 downloads emails to a local device<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Security_considerations\"><\/span>Security considerations<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">SMTP was originally designed without encryption. Modern implementations use additional security layers such as TLS to protect communication.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Without encryption, email content and credentials may be exposed during transmission.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Secure SMTP configurations use authentication and encrypted connections to prevent unauthorized access and interception.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Practical_use_cases\"><\/span>Practical use cases<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">SMTP is used for:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>sending emails from email clients (webmail or applications)<\/li>\n\n\n\n<li>relaying emails between mail servers<\/li>\n\n\n\n<li>sending automated system notifications<\/li>\n\n\n\n<li>integrating email functionality into applications and websites<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Practical_implications\"><\/span>Practical implications<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">SMTP is essential for email delivery but does not store or display messages.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Proper configuration of SMTP servers is required for reliable email delivery and to avoid issues such as spam filtering or rejected messages.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In modern hosting environments such as mybox, SMTP is typically used together with secure authentication and encryption.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Summary\"><\/span>Summary<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>SMTP is the core protocol for sending email messages across the internet. It enables communication between mail systems using a structured relay process and is essential for all outgoing email delivery.\n\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n<\/div>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"template":"","format":"standard","manualknowledgebasecat":[25],"manual_kb_tag":[1793,1794,1795,1796,1797,1798,1799,1800,1801,864,1802,1304,1803,1695,1804,1736,1805,1780,1806,1791,1792],"class_list":["post-821","manual_kb","type-manual_kb","status-publish","format-standard","hentry","manualknowledgebasecat-hosting","manual_kb_tag-email-messages","manual_kb_tag-smtp-session","manual_kb_tag-smtp-commands","manual_kb_tag-helo-command","manual_kb_tag-mail-from-command","manual_kb_tag-rcpt-to-command","manual_kb_tag-data-command","manual_kb_tag-email-server","manual_kb_tag-email-delivery","manual_kb_tag-email-protocol","manual_kb_tag-text-protocol","manual_kb_tag-simple-mail-transfer-protocol","manual_kb_tag-internet-email","manual_kb_tag-port-2","manual_kb_tag-sender-address","manual_kb_tag-protocols","manual_kb_tag-recipient-address","manual_kb_tag-quit-command","manual_kb_tag-smtp-protocol","manual_kb_tag-smtp","manual_kb_tag-send-email"],"_links":{"self":[{"href":"https:\/\/mybox.com\/help\/en\/wp-json\/wp\/v2\/manual_kb\/821","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mybox.com\/help\/en\/wp-json\/wp\/v2\/manual_kb"}],"about":[{"href":"https:\/\/mybox.com\/help\/en\/wp-json\/wp\/v2\/types\/manual_kb"}],"author":[{"embeddable":true,"href":"https:\/\/mybox.com\/help\/en\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":3,"href":"https:\/\/mybox.com\/help\/en\/wp-json\/wp\/v2\/manual_kb\/821\/revisions"}],"predecessor-version":[{"id":4718,"href":"https:\/\/mybox.com\/help\/en\/wp-json\/wp\/v2\/manual_kb\/821\/revisions\/4718"}],"wp:attachment":[{"href":"https:\/\/mybox.com\/help\/en\/wp-json\/wp\/v2\/media?parent=821"}],"wp:term":[{"taxonomy":"manualknowledgebasecat","embeddable":true,"href":"https:\/\/mybox.com\/help\/en\/wp-json\/wp\/v2\/manualknowledgebasecat?post=821"},{"taxonomy":"manual_kb_tag","embeddable":true,"href":"https:\/\/mybox.com\/help\/en\/wp-json\/wp\/v2\/manual_kb_tag?post=821"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}