Via 1 campaign mail is going and via another showing error


via 1 campaign, my email is going but via another campaign mail is going in error - for same mail acocunt

error coming is:

"503 Only one sender per message, please "

any ideas ?


I am not sure if this is an error you are getting from your ESP or maybe from Mautic. The emails you are sending, are they defined as transactional or marketing ? Marketing emails will only be sent once to each user, hwowver even so you would not be seeing this error.

It is giving you Only one sender per message, have you checked the email to make sure that in the advanced section there is only one email defined as the from address ?

What ESP are you using and do you have any limitations on it.

Hi Mike

Few observations & Crux of the issue/resolution:

  1. user created with different domain - “u1@domain1”
  2. Segment created using this user
  3. we are using SMTP of SendGrid
  4. campaign run using this segment and user - failed
  5. campaign run using different user, with domain2, and using same segment as above - failed
  6. i had different domain3 - we verified this domain in SendGrid
  7. created user ‘U2@domain3’ and created segment using this user
  8. campaign run using this segment and user - Passed
  9. campaign run using different user, with domain4, and using same segment as above (7) - PASSED

so meaning if we are using any domain in a single instance, it has to get white listed via SMTP provider, atleast with Sendgrid for that matter.


I think that you should try and use SendGrid API connection instead of SMTP as smtp is set to one sender whereas API you can use multiple senders, you would need to go to Settings (in SendGrid) and authenticate your different domains.

So you are saying that via API I can sent multiple senders instead of having with just sendgrid if I take SMTP route ?


Did you choose ‘sender is the owner’ in the advanced tab for the email?
If so, did you allow domain2 to be a sender at the Sendgrid dashboard?

I will test it out.


I have tried ‘sender is the owner’ and given From email using u1@domain1 - failed

Is this domain verified in sendgrid?
Dont use sender is the owner.
Plz try again just trying to send the email from domain1.

not goint…i think without domain approval via SMTP provider, it wont work.

Hey @joeyk

I think in SendGrid there are two ways to connect up, one is via smtp and in this way you define what the sender is (and the authentication is done on the specific sender, Sendgrid will send an email to the sender to verify that it is a real address), and then only this is the sender that can deliver e-mails, or via API and here you can authenticate on the domain level and once this is done you can authenticate on multiple domains and use any prefix to send e-mails.

I think that is why in this specific case the first mailer is being sent without an issue, but on the second mailer from domain2, mautic is passing through and SendGrid is expecting to get (that is already verified).

thats exactly what is happening…so now I am getting domain 2 verified in Send grid and will check and confirm back…

happy to see what experts have to say - @joeyk @mikew

New case arrived @mikew

I verified Domain 3

edited mail template; added From mail using user@domain3 - Mail sent - OK
edited mail template; added From mail using user@domain3, Enabled Owner as mailer - FAILED

why is that so ?


can you please try and connect up using API and not smtp.

In SendGrid go and generate yourself an API key and then in mautic choose API connection and put in the API key.

Then in SendGrid go and authenticate your domain - you will need to update your DNS records and then try

My best is you will happy working after this

are you sending the message as transactional or marketing

Sure. I will do that

But, my Domain3 is already verified in SendGrid

Will working via API will resolve this issue “edited mail template; added From mail using user@domain3, Enabled Owner as mailer - FAILED” - ?

I’m not sure why you want to set Mailer as owner.
Who is the owner of the contact? Do you have many owners?


From what I can understand yes this should resolve the issues. Best to go ahead and try. Make sure your domains are verified otherwise you will not be able to send through them, and to re-iterate make sure you are using API connection and not SMTP

I will check how to run campaign via API’s.