Using External SMTP Servers

Letting someone else handle your Zen Cart email

Generally web hosting accounts come with built-in email capabilities, but some people prefer not to use them. There are differing schools of thought about the merits of this approach. If you deem that this is the best practice for your business, the following information may be of help to you.

NOTE: If you are self-hosting on a local PC server for development purposes, remember that your ISP (internet provider) usually blocks outgoing traffic on port 25, which is commonly used for email. Anything on port 25 destined for any server other than the ISP’s own email server is generally blocked in order to control spam. You will need to choose another port (usually 587 or sometimes 465) and use SMTPAUTH and specify the correct SMTP server credentials.

See here: for a list of common server SMTP addresses if you’re using a “free” email service.

Note: Many customers prefer that you have a legitimate email address matching your domain name, not something like [email protected] which is rather less authentic-looking. Build credibility with your customers by getting proper email addresses to match your domain name!

NOTE: Using GMail, Office 365, Yahoo or GoDaddy for Zen Cart email are no longer recommended. You will have much less trouble choosing one of the real SMTP email service providers instead.


TLS is the modern preferred method for secure email transfer. To use TLS, simply set your port to 587.

In rare cases you may need to get really technical and also specify your TLS/SSL Certificate by adding a define for ‘SMTPAUTH_EMAIL_CERTIFICATE_CONTEXT’ in the extra_datafiles folder to supply your certificate-context, and in that same file also define SMTPAUTH_EMAIL_PROTOCOL to ‘starttls’. This is arguably more complicated and should be considered a last resort. Definitely try to sort out your email issues with your host before attempting StartTLS configuration!


Some hosts still haven’t configured their servers for TLS properly, so you may have to use the old SSL approach. If your host requires that you send email over SSL, then set your SMTP Port to 465.

Yahoo Hosting

If you are using Yahoo as a webhost, doing a search in the Yahoo help pages for PHP/Perl set up may help. Also setting up a tmp file in your Yahoo account may shed a bunch of light on things and give you answers right away as to why the e-mail isn’t sending.

  1. In your Yahoo control panel, check if the email address you are using is set as “Pop/Webmail”, and not just “Mail Administrator”. You may have to create a new one.
  2. The Zen Cart setting Emails must send from known domain must be set to Yes, and mail transport should be SMTPAUTH.
  3. In Zen Cart set the SMTP Host to Yahoo’s Outgoing (SMTP) Mail Server:
  4. SMTP Port 465 (You MIGHT be able to use 587, but may have to check with tech support first.)

If you’re hosting someplace other than Yahoo but trying to send email through your Yahoo email address, work with your hosting company to configure your DomainKeys and SPF settings to allow the emails to be accepted instead of being rejected as forged spam messages.

Google Mail / Gmail

NOTE: These instructions may no longer work. Your fallback option is to switch to one of the real SMTP email service providers.

Gmail / Google Apps Mail requires that your email communications occur over a secure channel, which means you need to send on port 587 for TLS.

Zen Cart supports this by using the following settings in Admin > Configuration > Email:


  • Email Transport: Gmail 1
  • SMTP Username: your gmail username
  • SMTP Password: your gmail password
  • SMTP Host:
  • SMTP Port 587

Google Apps Mail

  • Email Transport: SMTPAUTH
  • SMTP Username: your google-apps-mail username
  • SMTP Password: your google-apps-mail password
  • SMTP Host:
  • SMTP Port 587

Note: To use email (eg SMTPAUTH) with a Google mail account you need to enable allow less secure authentication inside your google account settings. (This name sounds much worse than it is; it’s still secure.)

Instructions on allowing less secure apps to use your account are provided here.

You may also need to visit the unlock CAPTCHA page to allow 3rd party access.

More technical information is available in Google’s Help Center.

You may have to have your host make some changes to your domain’s MX records if you are using Google hosted mail. Details for that are on Google’s help site.

You may also have to open your webserver’s firewall to allow access to Google’s servers and whatever port you’re using to communicate with them. Your hosting company’s server administrator will know how to identify the correct address and how to fix their firewall accordingly.

Office 365

NOTE: These instructions may no longer work. Your fallback option is to switch to one of the real SMTP email service providers.

Use the following settings in Admin > Configuration > Email:

  • Email Transport: smtpauth
  • SMTP Username: your Outlook email address
  • SMTP Password: your Outlook password
  • SMTP Host:
  • SMTP Port 587

And in your Office 365 account add the email as a safe sender of the account … essentially whitelisting yourself.

Other things to check:

  • Ensure your hoster is not blocking third party SMTP services.
  • Ensure your hoster is allowing the use of port 587.

Some additional steps will be required. Try Procedure 1 first, and if that doesn’t work, try Procedure 2.

Procedure 1:

Like Gmail, Office365 has a “switch” to configure to allow SMTP use:

  • In your Office365 admin panel, find the account for the Mailbox User you want to send “from”
  • Under that account’s “E-Mail” tab, find the “E-mail Apps” section and click Manage
  • Enable the “Authenticated SMTP” option, and save.
  • In Zen Cart set your SMTP Email Account Password to your mailbox password which you use to login to the account in Office365

Procedure 2:

If that isn’t enough, then you can also go one step further and create an “app-specific password” for your Store to use:

  • in Office365 enable MultiFactor Authentication for the entire company
  • then login to the specific mailbox account you wish to send From
  • in the Security Info section of the Account, Add an Application Password
  • For its “name” (which is just a description of where you use it) say “Online Store”, then click Next
  • you will see the password generated by Office365. Copy that password to your clipboard.
  • paste that password into your Zen Cart’s SMTP Email Account Password field instead of the usual password you use to login to the mailbox

You can get more help on this topic from Microsoft’s website

GoDaddy Hosting Plans

Note: As of the time of writing, GoDaddy has outsourced their email handling to Microsoft, so these instructions may not work.

  1. If using the default PHP setting for Email Transport method doesn’t work, try the following:
    • Use SMTP for your Email Transport setting instead.
    • Set your SMTP Email Server address to:, and the Mail Server Port to 25
    • GoDaddy’s odd configuration usually requires that you leave the SMTP mailbox and password fields blank. (Alternatively use enter your email address as the mailbox, and supply the corresponding password.)
    • Set the Emails must send from known domain to yes. (This is required so that the GD mail servers don’t reject your emails)
    • For your “Sent FROM” email address, use an email address that matches the domain name of your website. ie: if your website is, then use something like [email protected] as your Sent From email address (otherwise GD may reject your emails).
    • Do not send an email “to yourself”, “from yourself” when testing.
  2. Set your Max Email limit:
    • If you have a GoDaddy hosting plan and plan to use it for sending emails from your Zen Cart site, you should check your email account list and set the smtp relay transmissions per day to the max of 250/day instead of the default of 0/day.

Email Service Providers

SMTP Email Service Providers that Zen Cart users have had success with are:

  • SMTP2Go
  • Mailgun
  • SendGrid
  • Mandrill (by MailChimp)


  1. If this value does not appear in your list of Email Transport options, see this forum post↩︎

Still have questions? Use the Search box in the upper right, or try the full list of FAQs. If you can't find it there, head over to the Zen Cart support forum and ask there in the appropriate subforum. In your post, please include your Zen Cart and PHP versions, and a link to your site.

Is there an error or omission on this page? Please post to General Questions on the support forum. Or, if you'd like to open a pull request, just review the guidelines and get started. You can even PR right here.
Last modified August 27, 2023 by Scott C Wilson (43f0efa).