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Introducing a new kind of SMTP Service

GMass SMTP service

If you have a website, app, or blog, you’ve likely connected to a transactional email service through a transactional email API or an SMTP service. Popular SMTP services include SendGrid, Mailgun, and Amazon SES. You can now use the GMass SMTP service instead.

What is a transactional email?

Transactional emails are emails that are sent after a user takes an action in your app.

Examples include:

  • confirmation emails after filling out a form
  • shipping notifications after an order is shipped
  • password reset emails

Any email that is sent to your user to facilitate a “transaction”. And by “transaction”, I don’t mean a financial transaction. I mean, any transaction on your website, including filling out a form, placing an order, signing up, etc.

Today we are introducing a different kind of SMTP service — a service that sends your transactional email through your Google account. Just relay your emails through smtp.gmass.co and your email will be sent through your own Gmail or Google Workspace account. You’ll still get analytics on opens and clicks like you’re used to with other SMTP services.

Why is the GMass SMTP relay better than traditional SMTP services?

There are several advantages to using our new SMTP relay service.

  1. Searching: With every transactional email now logged to the Sent Mail folder of your Gmail account, you can easily search for any email by subject, body, recipient address, sender address, and more. For example, if you’re using this service to send “Your order has shipped” notifications, and the body of the email includes the order number and other details, you can now search for any transactional email just by searching in Gmail. Traditional SMTP services like SendGrid and others have poor search capabilities, and some even charge extra if you want to search beyond a few days worth of history.
  2. Deliverability: The default setup when you sign up for services with SendGrid or others is you’re put into a shared pool of IP addresses. Often times, those IP addresses are blacklisted in several places, and deliverability is poor. When you complain to the service, they ask you to upgrade (and pay for) a dedicated IP address. They win and you lose. With the GMass SMTP relay, your emails are sent from your Google account and from Google’s IP addresses. Nobody blocks Google’s IPs.
  3. Ease of setup: When you start sending through a new SMTP service, you have to enter in DNS records, set up SPF, DKIM, and other protocols with the service provider. With the GMass SMTP relay, as long as your email service has been configured with Google Workspace already, there’s nothing else to set up.
  4. Easily turn transactional emails into marketing campaigns: Let’s say you’re using the service to send “Your order has shipped” emails. Using the GMass Chrome extension’s “build email list” button, you can easily extract all the recipient addresses of the “Your order has shipped” emails, and send a campaign to anyone that has received a past order from you. No more importing/exporting data between your order entry system and your email marketing system.
  5. Speed: Given that Google controls about half of the world’s Inboxes, there is the lowest latency possible sending email from a Google account to a Google account.

Know your limits

The GMass SMTP Service should only be used to send email from your website/app if you have low-volume needs. If you have a gmail.com account, you can send about 500 total emails/day, and if you have a Google Workspace account, you can send about 2,000 emails/day. If you need to send more transactional email than your account allows, then you should use a regular service like SendGrid, Mailgun, or Amazon SES rather than the GMass SMTP service.

Is this for me?

GMass offers several “SMTP” options, so it’s easy to get confused about whether this new service is for you.

The GMass SMTP Service is not for you if:

  1. You’re using GMass to send out campaigns and you want to get around Gmail’s limits. For that, you have to integrate with an SMTP service like SendGrid, Mailgun, or JangoSMTP. More information.
  2. Your only email sending needs are for your marketing campaigns or cold email campaigns.
  3. You need to send more transactional email per day than your Google account allows (about 500 for a gmail.com account and about 2,000 for a Google Workspace account).

The GMass SMTP service is for you if:

  1. You have a website or app that sends emails right now through another transactional email service like SendGrid, Mailgun, or JangoSMTP.
  2. You have devices like printers or scanners on your network that need an SMTP service.
  3. You use an external email client that has its SMTP server set to some other service.
  4. You have a WordPress site and are using an SMTP plugin like WP Mail SMTP. In each of these cases, you can relay your email through smtp.gmass.co instead of the SMTP server you’re currently using, if your volume needs are below what your Gmail account allows sending.

Why can’t you use the GMass SMTP service with the GMass extension for Gmail?

The GMass extension adds buttons inside your Gmail account so you can send campaigns directly inside Gmail. Under the standard setup, the number of emails you can send is limited to what your Gmail or Google Workspace account allows. Typically that’s 500/day for gmail.com accounts and 2,000/day for Google Workspace accounts. If you connect your GMass account to an outside SMTP service like SendGrid or Mailgun, you can break those limits and send more email.

So now that GMass has its own SMTP service, why can’t you connect your GMass account to that service to break Gmail’s limits?

Because the GMass SMTP service sends emails through your Gmail account. When you send emails through an external SMTP service like SendGrid or Mailgun, your emails are sent from their networks over their IP addresses. When you send emails through the GMass SMTP service, your emails are sent directly from Google’s IP addresses from your Gmail account, so sending through our SMTP service subjects you to the standard sending limits of your Gmail account.

Getting started

Set your website, app, desktop tool, or other email system to send email through this SMTP server:


You can connect on any of the following TCP/IP ports:

25, 465, 587, or 2525

Use basic SMTP authentication. Your credentials are:

Username: gmass (everyone’s username is “gmass”)
Password: Your API key created from your account’s settings

You can connect via TLS (Transport Layer Security) to any of the above ports.

Set your tracking preferences for open and click tracking in your account settings.


The GMass SMTP Service is free for everyone right now. You can send up to your Google account’s daily limits without subscribing to a paid GMass plan.

Doesn’t Gmail already provide an SMTP relay?

Yes Gmail already offers an SMTP relay, but it’s difficult to use and doesn’t track your emails. You can relay emails through smtp-relay.gmail.com, as Google explains, and send emails directly from your Gmail account. So why use smtp.gmass.co when you can use smtp-relay.gmail.com?

The native Gmail SMTP relay has these disadvantages:

  1. It’s complicated to set up. You have to turn on settings in your Google account like “Allow less secure apps”. (Check out our Gmail SMTP settings article to learn more.)
  2. It exposes your Google account username and password.
  3. It doesn’t provide analytics like open and click tracking.
  4. It doesn’t provide an audit trail of messages.

More examples of transactional email, from yours truly

Here are examples of transactional email that I’m personally sending through the GMass SMTP service:

  • “Welcome to GMass” emails whenever somebody signs up.
  • A “You have subscribed!” email after somebody subscribes to a paid plan.
  • A “Your campaign has completed” email after a campaign is finished sending.
  • A “Disk space low” email to me and our sysadmins if the hard drive on one of the GMass servers is low on space.
  • A “Your job has failed” email to me and our sysadmins if our database server throws any kind of error.

What kinds of transactional email do you send?

Email marketing, cold email, and mail merge inside Gmail

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  1. I think what makes Gmass better than all other software is simply the amount of crazy value it delivers. I mean delivery test, warmup, verification and now this. I’m never looking at another email service because this does everything and does it better than any other similar services i’ve used so far.

  2. I use an app called Calendly to schedule appointments. After the appointment their app send an email out thanking person for meeting with me. I do not get copy of this email. Is this new SMTP service send the email and leave a copy in my Gmail send folder? Or, will it cc me on that email?

    1. I’m familiar with Calendly but I don’t think they let you set your own SMTP server for Calendly notifications, so without that ability, you couldn’t use our SMTP service with them. But, if they ever did, then what you are wanting to do would work.

  3. Does this work for sending from email aliases, meaning from addon domains attached to the primary domain used for Google Workspaces?

    Thank you,

    1. Yes. Any alias “from” addresses that are configured in your Google account can be used as the From Address with our SMTP service. If, however, you specify a From Address in your SMTP relay message that is NOT configured, then Google will overwrite your specified From Address with your default Gmail account address as the From Address.

    1. Not for long. Eventually it will operate under the same model as our regular campaign service, where it’s free for 50 emails/day and you have to upgrade to send beyond that.

  4. This looked ideal as most of my transactional stuff was going to SPAM folders. So I connected my account to your tester and that worked. Then I tried to connect my autoresponder (ListMailPro) to smtp.gmass.co using my API key as the password as instructed. It quite simply doesn’t get through ad gives me a “can’t connect to smtp.gmass.co” error message together with “bad password”. I have requested support but not had an answer yet. Is there something really obvious I am doing wrong?

  5. This looked ideal as most of my transactional stuff was going to SPAM folders. So I connected my account to your tester and that worked. Then I tried to connect my autoresponder (ListMailPro) to smtp.gmass.co using my API key as the password as instructed. It quite simply doesn’t get through ad gives me a “can’t connect to smtp.gmass.co” error message together with “bad password”. I have requested support but not had an answer yet. Is there something really obvious I am doing wrong?

  6. So you have the regular Gmass for cold outreach that you manage using the Gmass extension; then there’s this GMass SMTP feature.

    What is the benefit of Gmass SMPT if it operates under the same limits as the Gmail/Workspace account? If it has the same limits, why bother and not just use the main Gmass function instead?

    Isn’t this a feature to add to the bloat?

  7. These days Gmass seems to be not performing at all. It goes DOWN / No email deliveribility is shown and its been happening over 1 month now and daily same thing.
    Is this going to work out or some alternates maybe…??

  8. Hi! Love Gmass quite a bit! My campaigns seem to be going through your SMTP relay even though I use Sendgrid and have it set up correctly. Both Sendgrid and GMass are charging me for my emails. I believe this was accidentally enabled. How does one stop using this SMTP relay without canceling the account?

  9. my requirement is to send 4000-5000 mail per day, through my business email (not gmail) like abc@ xyz.com. how can we do this. plz suggest me detail

    1. Hi Vijay,

      The GMass subscription plan you choose doesn’t have an effect on the sending your account is able to per day. The sending limit is something that is enforced by Gmail, not by GMass. According to Google, regular Workspace accounts are limited to a maximum of 2900 emails per day. But other factors like the age of the account, the content of the Campaign, or reputation of the domain can affect your sending limit and varies from one account to another.
      You would need to configure your account with an external SMTP server if you’d like to send high volume campaigns without Gmail-imposed sending limits. See: https://www.gmass.co/blog/unlimited-mail-merge-sending-gmail/  

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