Using an external SMTP server to send unlimited emails with Gmail and GMass

This article is a guide for GMass users that want to start using SMTP-based sending for their email campaigns in Gmail using GMass. Last week I announced this feature was coming, and starting today, we’re asking users to begin testing.

Update on 10/25/17: Note that this feature has now been officially launched! Go over to the official guide to unlimited mail merge in Gmail!

The advantage of this setup are:

  • The ability to send virtually unlimited emails and not be constrained by Gmail’s sending limits.
  • No risk of an account being suspended by Google.

The disadvantages of this setup are potentially:

  • A slight decrease in deliverability, although from our testing, we’ve found the deliverability using Sendgrid as the SMTP server to be just as high as sending natively from Google.

Choosing an SMTP server

You have two choices to connect your GMass account to an SMTP server:

  1. If your email sending meets certain criteria, you can use my SMTP server, which is a high volume server with Sendgrid. Your email sends must be either a) non-commercial in nature (like school groups, membership clubs, social causes, churches) or b) completely organically developed. So, your emails can be of a commercial nature if your list is completely organic. If that’s the case, you’re welcome to use the SMTP service I have with my Sendgrid account. Contact us at to make this request, and state the nature of your email sending.
  2. If your email does not match this criteria, or you just want to use your own SMTP service, then feel free to set up an account on your own with SendgridJangoSMTPMailjet, or any other SMTP service provider. Your company may even have its own SMTP server that you can use. In a future post, I’ll be analyzing the popular SMTP providers, also known as transactional email services, and explaining which ones I think are the best and worst. Once you set up an account with an SMTP service provider, you’ll have to configure the account in certain ways. Read on…

Configuring your SMTP service account

  1. GMass will connect without TLS/SSL to the SMTP server on the port of your choice. Most SMTP services allow you to connect on ports 25 and 2525 at a minimum.
  2. Ensure that open and click tracking are turned OFF with the SMTP server service. In fact, the SMTP server shouldn’t alter the message at all. It should just pass it through. This is because GMass will add the tracking for you if you set your tracking this way, and we don’t want the emails to be “double” tracked. Screenshot from Sendgrid:
    Sendgrid Tracking
  3. Ensure there are no quota restrictions on your SMTP account, or if there are, that they are sufficient to handle your GMass campaigns.
  4. Check to see what Envelope From, also known as MAIL-FROM or RETURN-PATH address your SMTP service will use when relaying your email. Most transactional email services like Sendgrid use a domain by default, which makes it so you don’t necessarily have to alter your SPF records. Some SMTP services require domain verification, because the domain in your From Address will be the domain in the MAIL-FROM. Just be aware of this. You may need to alter your SPF, DKIM, and DMARC records.
  5. Ensure that Bounce Notifications are on. Set them to go to the From Address. This will allow GMass to process your bounces, just like normal. Not all SMTP services have this capability. Sendgrid and JangoSMTP do. Mailgun and Mailjet do not. Screenshot from Sendgrid:
    Sendgrid Bounce Settings

How to set your GMass account to send emails through an external SMTP server

GMass SMTP Configuration
Configure your GMass account to send via an external SMTP server instead of your Google account. The Sendgrid credentials show above are not real.
  1. First, reload Gmail in your Chrome browser to make sure you have the latest version of GMass.
  2. Click Compose to launch a new window.
  3. Set the To field to
  4. Set the Subject to the word set. Wait a second for the form to appear in the Message area.
  5. Enter the SMTP server, port, username, and password after the colons.
  6. Hit the GMass button. Do not hit the Send button.

GMass will attempt to relay a test message through the server to yourself. If successful, the SMTP server will be set for your account.

To clear out the SMTP settings, set the Subject to “clear”. To view the SMTP setting currently on your account, set the Subject to “status”.


15 Replies to “Using an external SMTP server to send unlimited emails with Gmail and GMass”

  1. Domagoj Marenic

    Does external smtp work on hosting smtp, and is available to google suit services? I see the use of you did not specify, and it allows all google users 10,000 email messages per day which is quite enough for most, and stays in and continues to send mail via gmail service.

  2. Whitney Ludwig

    getting an error when i try to enter the smtp server, port, username, and password.

    I’m using gmail and sendgrid.
    error occurs when I press the gmass button after filling out the form to send.

    error is:
    Your GMass request failed. Error details: Index was outside the bounds of the array.

  3. Josh

    Would it be possible to see any stats on deliverability with the 3rd party? We tried with sendgrind before and this reduced deliverability 90% over using gmail servers.

    Great tool 🙂 Much thanks!!

  4. adam sert

    when i do all configuraion and and click at Gmass , it give me that message

    Your GMass request failed. Error details: Index was outside the bounds of the array.

    • Maya Quijada

      This is a temporary error and should go away if you refresh Gmail in Chrome and try again (don’t worry, you won’t lose your work). However, it depends what you’re trying to do – if that doesn’t work, will you send us an email at Our support team will give you a hand.

  5. Lee Robertson

    I can’t say much right now I have to work with GMass a little longer, I still trying to understand how it works. The little I know about GMass I love it!

  6. Carol

    I have been seeing below error in my account..

    Your GMass request failed. Error details: The SMTP server has unexpectedly disconnected.

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