{"id":35672,"date":"2019-07-17T06:22:43","date_gmt":"2019-07-17T06:22:43","guid":{"rendered":"https:\/\/wp.lvh.me\/blog\/2019\/07\/17\/headers-how-to-show-them-in-your-emails-and-avoid-problems\/"},"modified":"2026-10-15T17:26:19","modified_gmt":"2026-10-15T17:26:19","slug":"headers-how-to-show-them-in-your-emails-and-avoid-problems","status":"publish","type":"post","link":"https:\/\/mailrelay.com\/en\/blog\/2019\/07\/17\/headers-how-to-show-them-in-your-emails-and-avoid-problems\/","title":{"rendered":"Email Headers: How to Show Them and Avoid Delivery Problems"},"content":{"rendered":"\n

Mailings and newsletters are much more complex than they look at first glance<\/strong>, especially when we use a more or less customized design instead of just sending plain-text emails.<\/p>\n\n

More than once (I’m sure it’s happened to you too), when I’ve launched an email marketing campaign, I’ve run into the problem of some of my emails ending up in spam. One of the causes of this problem? Errors in the header…<\/strong><\/p>\n\n

That’s the main reason I wrote this article: to tell you how I managed to avoid this by optimizing my email headers, and how the Mailrelay support team helped me solve it.<\/p>\n\n\n

\u00b7 Email headers: Features and functions<\/h2>\n\n

It’s only natural that when you send a mailing<\/a>, you wonder whether the recipient will receive your emails correctly. In fact, we often find ourselves needing to check the status of a send.<\/p>\n\n

That’s why, before you start your email marketing campaign and send your emails, it’s very important that you understand what email headers are and what they’re for, since they will give you:<\/p>\n\n

    \n
  1. All the relevant information about the path each email has taken.<\/li>\n\n\n\n
  2. The servers the emails have passed through.<\/li>\n\n\n\n
  3. What errors<\/strong> occurred along the way.<\/li>\n<\/ol>\n\n

    To find out what happens to your mailings and newsletters once they’ve been sent, there are only a few options:<\/p>\n\n

      \n
    1. Mail server logs (which only the administrators of the email accounts can access).<\/li>\n\n\n\n
    2. The statistics available in email marketing tools like Mailrelay (which let us detect errors up to a point).<\/li>\n\n\n\n
    3. Email headers (accessible to everyone).<\/li>\n<\/ol>\n\n

      \u201cDon’t be intimidated by the code and HTML side of things. Although headers can be hard to read, there are tools that help us interpret them and analyze what happened to each of our emails.\u201d<\/strong><\/em><\/p>\n\n

      \u25ba Header elements<\/h3>\n\n

      As we’ve seen, headers let you analyze information about each of the servers the email has passed through (among other things), bearing in mind that every email passes through at least four different servers.<\/p>\n\n

      So all the information collected here covers the journey from the moment the sender clicks \u201csend\u201d in their email client or email marketing tool until that email appears in the recipient’s inbox.<\/p>\n\n

      Other interesting data you can get includes:<\/p>\n\n

        \n
      1. Email format.<\/li>\n\n\n\n
      2. Name of the email client used.<\/li>\n\n\n\n
      3. Origin (whether it’s a corporate email or not).<\/li>\n<\/ol>\n\n
        \"Example<\/figure>\n\n

        <\/p>\n\n

        So the information in an email header has to do with you (the sender of the message), such as the tool you used to send it (in my case, Mailrelay), a list of technical details (message ID or spam status) and the list of all the servers the email passes through before reaching your recipients.<\/p>\n\n

        These are some of the fields you’ll find in your email headers:<\/p>\n\n

          \n
        1. From:<\/strong> The sender of the message.<\/li>\n\n\n\n
        2. Subject:<\/strong> The subject of the email.<\/li>\n\n\n\n
        3. Date:<\/strong> The date and time it was sent.<\/li>\n\n\n\n
        4. To:<\/strong> The recipient, although their email address doesn’t have to appear.<\/li>\n\n\n\n
        5. Return-Path:<\/strong> The account the email is returned to, or \u201creply to\u201d.<\/li>\n\n\n\n
        6. Delivery date:<\/strong> The date and time your email client received the message.<\/li>\n\n\n\n
        7. Received:<\/strong> This is the most important one, because it shows all the servers and computers your email has passed through.<\/li>\n\n\n\n
        8. Message-id:<\/strong> When the message is created, the system generates a string, which can easily be forged.<\/li>\n\n\n\n
        9. X-Spam-Status and Level:<\/strong> Your service generates a spam score.<\/li>\n\n\n\n
        10. Message body:<\/strong> The content of the email.<\/li>\n<\/ol>\n\n

          \u201cHere’s an interesting fact: many spammers tamper with headers, altering the \u201cfrom\u201d and \u201creturn-path\u201d fields to hide behind fake identities.\u201d <\/strong><\/em><\/p>\n\n

          The only fields that can’t be tampered with are the \u201creceived\u201d fields, where the outgoing IP is generated automatically by the recipient’s server.<\/p>\n\n

          \"Why<\/figure>\n\n

          <\/p>\n\n

          \u25ba Why show the header of an email?<\/h3>\n\n

          I remember that a year ago I launched an email marketing campaign<\/a> for my blog Dise\u00f1o Creativo<\/strong>, with the goal of winning new clients. I had a strong database<\/a> and had segmented my audience very well so I could send several different messages to each buyer persona.<\/p>\n\n

          However, after sending the emails and analyzing some tracking reports<\/a> in Mailrelay<\/strong>, I realized that some people hadn’t opened my email. The reason? The emails had landed in spam and, above all, in Gmail’s Promotions folder.<\/p>\n\n

          This can happen for many reasons, but in my case the problem was caused precisely by errors in the header’s HTML code.<\/p>\n\n

          Since HTML isn’t my strong suit, I contacted support and sent them my newsletter<\/strong>, forwarding the original email so they could analyze what was going wrong with the send.<\/p>\n\n

          That seemed like the simplest approach. The thing is, one of the reasons to show the headers is that it’s the only way a technical support team can help you work out whether the error might be coming from the header itself. In conclusion\u2026<\/p>\n\n

          \u201cIf you want support to be able to analyze the header code of your mailings or newsletters, you’ll need to turn on the option to show the header in your emails.\u201d<\/strong><\/em><\/p>\n\n

          So, to recap everything I’ve been telling you, showing them is useful for:<\/p>\n\n

            \n
          1. Tracing emails to prevent any intrusion.<\/strong> As I mentioned earlier, some parts of the header can be tampered with by hackers, and this can be detected through the data generated in the headers’ HTML.<\/li>\n\n\n\n
          2. Making emails easier to read for blind people.<\/strong> They use assistive devices that read the header code to interpret the email.<\/li>\n\n\n\n
          3. Keeping the email out of the spam folder<\/strong>. That’s why we provide these headers to support teams like Mailrelay’s, so they can solve technical or HTML code problems.<\/li>\n<\/ol>\n\n
            \"How<\/figure>\n\n

            <\/p>\n\n

            \u00b7 How to show the headers in your email client?<\/h2>\n\n

            If you’re also having deliverability problems with your emails, and everything else seems to be in order (at least as far as you know), I recommend you consider the header as a possible trigger.<\/p>\n\n

            But… what should you do if code isn’t your thing and you don’t know how to show your email headers<\/strong> either? Well, don’t panic, because that’s exactly what we’re going to look at now \ud83d\ude42<\/p>\n\n

            First, you’ll need to find the header of the original email so you can send it to your email marketing tool’s technical support team or straight to your trusted developer.<\/p>\n\n

            Below, I’ll show you where to find this information in the 4 most widely used email services (since it varies in each one): Gmail, Hotmail, Outlook and Thunderbird.<\/p>\n\n

            \u25ba Gmail<\/h3>\n\n

            If you use Gmail, which is quite likely, follow these steps to find the header of an email:<\/p>\n\n

              \n
            1. Open the message you want to inspect.<\/li>\n\n\n\n
            2. Once it’s open, on the right, right next to the \u2018reply\u2019<\/strong> button, open the drop-down menu and click \u201cshow original\u201d<\/strong>.<\/li>\n\n\n\n
            3. Then copy all the text and paste it into one of the tools you’ve chosen beforehand, in the \u2018paste email header here\u2019 option.<\/li>\n<\/ol>\n\n

              And that’s it! Now you can show the header and spot errors (if there are any).<\/p>\n\n

              \"Gmail<\/figure>\n\n

              <\/p>\n\n

              \u25ba Hotmail \/ Outlook<\/h3>\n\n

              For Hotmail, these are the steps to follow to find out where an email’s header is:<\/p>\n\n

                \n
              1. Open the email you want to inspect.<\/li>\n\n\n\n
              2. Click the three-dot menu<\/li>\n\n\n\n
              3. Click the “view message source” button.<\/li>\n<\/ol>\n\n
                \"Outlook<\/figure>\n\n

                <\/p>\n\n

                When you select this option, you’ll see the email headers in a new window or tab, like this:<\/p>\n\n

                \"Outlook<\/figure>\n\n

                <\/p>\n\n

                \u25ba Outlook Desktop<\/h3>\n\n

                If your email service provider<\/a> is Outlook for Office 365, 2016, 2013 or 2010, you’ll find your email headers like this:<\/p>\n\n

                  \n
                1. Double-click the email to open it outside the reading pane.<\/li>\n\n\n\n
                2. Now click \u2018file\u2019 and then \u2018properties\u2019.<\/li>\n<\/ol>\n\n

                  You’ll find the header information in the \u2018Internet headers\u2019<\/strong> box.<\/p>\n\n

                  \u25ba Thunderbird<\/h3>\n\n

                  If you want to view your email headers in Mozilla Thunderbird, follow these steps:<\/p>\n\n

                    \n
                  1. Open the email you want to check.<\/li>\n\n\n\n
                  2. Click the “More”<\/strong> drop-down menu<\/li>\n\n\n\n
                  3. And then “View Source”<\/strong><\/li>\n<\/ol>\n\n
                    \"Thunderbird<\/figure>\n\n

                    <\/p>\n\n

                    \u00b7 Tools to analyze your email headers<\/h2>\n\n

                    This is a clear example of why we should place our trust in technical support professionals to optimize our campaigns.<\/p>\n\n

                    In my case, I didn’t hesitate to trust Mailrelay’s technical support to optimize my newsletters<\/strong> right away and fix the code errors that were keeping my emails from reaching their destination.<\/p>\n\n

                    However, if you know a bit about programming and want to fix these errors yourself, there are some free tools that will help you track and analyze the HTML code of an original email in detail.<\/p>\n\n

                    I’ll tell you about 3 tools: Google Admin Toolbox Messageheader, Web Developer for Firefox and MxToolbox Email Header Analyzer.<\/p>\n\n

                    \u25ba Google Admin Toolbox Messageheader<\/h3>\n\n

                    Among other things, this tool helps you identify:<\/p>\n\n

                      \n
                    1. Delays in receiving emails.<\/li>\n\n\n\n
                    2. The reason for the delay.<\/li>\n\n\n\n
                    3. Who is responsible.<\/li>\n<\/ol>\n\n
                      \"Email<\/figure>\n\n

                      <\/p>\n\n

                      \u25ba Web Developer for Firefox<\/h3>\n\n

                      This is a Firefox extension<\/a> that appears as a toolbar at the top of the Firefox window.<\/p>\n\n

                      It has buttons with different functions, notably the \u2018Information\u2019 and \u2018view source\u2019 buttons, which you can use to get information about a page’s elements and view its source code.<\/p>\n\n

                      MxToolbox Email Header Analyzer<\/h3>\n\n

                      Web Sniffer, the tool we used to recommend in this section, is no longer available. A free alternative is the MxToolbox Email Header Analyzer<\/a>: you copy the email’s full header, paste it into the analyzer, and it shows you each hop between servers, how long each one took and the results of the SPF, DKIM and DMARC checks.<\/p>\n\n

                      It works in your browser, with nothing to install, and it’s useful for finding out why an email arrived late or ended up in the spam folder. If you want to review what each field means, check out our glossary entry on email headers<\/a>.<\/p>\n\n

                      \u00b7 In conclusion…<\/h2>\n\n

                      When we’re thinking about an email marketing strategy for our business, it’s very common to worry about how to attract subscribers, how much the email marketing tool will cost or how to manage and segment the database, but\u2026 what about the more technical side?<\/p>\n\n

                      If you have a developer, or you know your way around the subject, putting together newsletters and handling server data and the like will be a piece of cake\u2026 But if that’s not your case, or you simply don’t have time to dwell on this part, it’s essential that you know all the shortcuts and make things easy for the people who can help you.<\/p>\n\n

                      That’s why in this article I’ve shown you the different options we have for showing our email headers, as well as tools for analyzing possible errors.<\/p>\n\n

                      What other delivery errors have you run into with your email marketing sends? Did you know that headers can be a reason our emails end up in spam?<\/p>\n\n

                      \"Teresa<\/a><\/figure>\n\n

                      <\/p>\n","protected":false},"excerpt":{"rendered":"

                      Mailings and newsletters are much more complex than they look at first glance, especially when we use a more or less customized design instead of just sending plain-text emails. More than once (I’m sure it’s happened to you too), when I’ve launched an email marketing campaign, I’ve run into the problem of some of my […]<\/p>\n","protected":false},"author":2,"featured_media":21496,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_uag_custom_page_level_css":"","footnotes":""},"categories":[588],"tags":[],"class_list":["post-35672","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-without-category"],"yoast_head":"\nEmail Headers: How to Show Them Without Problems in 2026<\/title>\n<meta name=\"description\" content=\"Discover everything you need to know about your email headers and the best solutions with Mailrelay. 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