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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 three 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 support@gmass.zendesk.com 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.
  3. If you’re technically inclined, you can set up your own SMTP server on your own server. If you’re running Linux, here’s how to set up an SMTP service on a Linux server.

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 sendgrid.net 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

See this post on connecting your SMTP system to your GMass account.


  1. Fantastic Ajay, top notch as usual. How can I sign up to use yours?

    Going to upgrade my plan too.
    So excited this tools is amazing.


      1. So I have set up my gmass.co account to work with Sendgrid smtp and my account has been verified. I decided to test it by using 58 addresses that had been blocked by gmail because they said I was over limit. I loaded the addresses into the “To” field and hit the gmass button to send them. They were scheduled to be sent on Monday. Here’s my question: Will they automatically be sent using the smtp link to Sendgrid or I am supposed to do something that makes that happen? I thought that would be an option to send either through my smtp account or the regular gmass account but I was never given that choice. What did I do wrong, if anything? Thank you.

      2. Hi need help , i have sent 4000 mails last night only 495 five sent due to servers issue , it gmass server not allowed higher volume mails . what will do , are we need to get external servers

          1. Can you walk me through the steps or send me a good link on how to connect sendgrid to gmass successfully

  2. Does external smtp work on hosting smtp, and smtp-relay.gmail.com is available to google suit services? I see the use of smtp-relay.gmail.com 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.

  3. 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.

  4. 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!!

  5. 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.

    1. 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 support@gmass.zendesk.com? Our support team will give you a hand.

  6. 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!

      1. When I GMass Amazon email addresses (20 at a time), my emails look like they went through just fine in my mail application in the sent folder, but I know that the recipient never received it. Do you know why Maya?

        1. Did you ever get your GMass Amazon SES connection to work?

          I’m having trouble with mine, it gives the error Error: The SmtpClient is not connected. and Error: Timeout waiting for data from client. after sending 400 emails max each time.

          1. Hello Stacy… did u GMass Amazon SES connection work ? I am also getting same error constantly

  7. I have been seeing below error in my account..

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

  8. I need send 50 thousand emails from 50 my own mailbox’s (email id created using my own domain) per day using gmail smtp. is it possible?

    1. If you wish to use Gmail servers to send your emails, then you will be bound by a Google imposed sending limit. This limit varies from one account to another and are not set in stone.

      If you have 50,000 emails to send using 50 email accounts, then 1000 emails per day per account is possible as it would be below the official limits for G Suite accounts which is set at 2,000 emails/day.

      To learn more about these limits, please see https://www.gmass.co/blog/how-many-emails-can-you-really-send-with-gmass-and-gmail/

  9. Just a heads up, if you use SendGrid most of your e-mails will end up in your recipients’ Promotions tab. I used the Inbox/Spam tool and everything sent with SendGrid ended up in promotions, not to mentions AOL and Yahoo blocked me. Just keep using the default Gmail option and send in batches over a few days.

    1. Hi Ryan,

      Thanks for the suggestion for other users. Where emails land would be dependent on a lot of factors: mainly the SendGrid server’s IP, the content as well as the email address where the emails originate from.

      You’re correct in suggesting to using the default Gmail option spread over a few days to ensure maximum deliverability as your emails would be sent through Google’s own servers which is highly trusted by most, if not all, platforms and filters.

    1. Hi Boyd,

      This appears to be an SMTP error. Kindly check your SMTP account to see what is causing that error.

  10. I have now sent 6 emails over the course of the last 8 days, Still no response. It says to have an STMP Server Added sent your credentials to SMTP@gmass.co Subject: Set and then your log in info. I have done so now 6 times. Each time waiting more than 24 hours between them. I Like gmass, but my business is getting it hard by being unable to send the amount that i need. I do marketiing for many companies and i need to be able to send 50,000-70,000 emails per week. But i was going to test your services first before i got a larger SMTP account. I have Mail Jet premium that allows me to send i believe 30,000 emails a month if i am not mistaking. I have sent all the info and still nothing. Waiting 24 hours to send 2000 emails when i need to send 10,000 and have limited days to market the events that we are doing is stressful. But what is most stresfull is that i have’t even so much as got a reply. Not even an automatic reply lol. Please help me, or update me on a time that it will take for you to process my request so i can determine my next move of staying or going until you can complete it. Again, love the ease and the features are smooth. Simple but easy to understand and gets the job done.

  11. hi please help me
    i have sent 4000 mails through gmass . but only 500 sent due to server issue . what is the reason and solutions.

  12. When connecting to Sendgrid SMTP, you talk about sending unlimited emails but even if you had a large plan with Sendgrid, is there not some kind of throttling that would limit your emails?

    If for example I wanted to send to a list of 10,000 or 30,000 contacts at a time in Gmass, and I had a large plan with Sendgrid that allowed me to send say 100k emails per month, would all those emails actually send?

  13. Are there any special instructions for setting up an email address on your own domain through Gmail? I have configured myemail@mydomain.com to be used through my Gmail account and GMass works fine but I am hitting Gmail’s daily limit. When I try to set GMass to use my external SMTP based on the instructions above I can an authentication error. Is this because my username is myemail@mydomain.com as opposed to the Gmail address I am subscribed to GMass through?

    1. Hi Hussain,

      You would need to set up the external SMTP using your Gmail account. When setting the SMTP settings, please make sure that you have selected your main account where you have the alias rather than the actual alias in your compose window.

  14. if I try my SMTP server on your test page

    everything is OK. But if I try co connect with my gmail there is a problem.

    “Uh oh, something went wrong. Here is the detailed error: General Exception From/Sender name is not valid Try the SMTP Test Tool to troubleshoot the issue.”

  15. I’m impressed, I need to say. Really rarely do I encounter a weblog that’s both educative and entertaining, and let me let you know, you have hit the nail on the head. Your idea is outstanding; the difficulty is something that not enough people are talking intelligently about. I am very happy that I stumbled across this in my seek for something referring to this.

    1. Hi Shekhar,

      You can set up more than one SMTP server, however, you can only connect one SMTP to GMass at a time. So you can connect one SMTP, do your sending and then connect the other to continue sending a different batch.

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