Mandrill for Outgoing WHMCS Emails


We are starting to use Mandrill here at WebUp, we configured our company emails on Outlook and it works perfectly.

But on WHMCS we are having some issues implementing it:

WHMCS is confirming the emails being sent through SMTP, and we receive the test emails.

But those emails aren't being processed by Mandrill.

Can someone that uses Mandrill with WHMCS, give us a tip on how to solve this?

- Henrique


New Member
We haven't seen any issues using Mandrill for WHMCS. I'm fairly sure we use an API key as the password.


New Member
Verified Provider
Glad to see everything is working out for you now. We are considering moving our email to Office365 but Mandrill seems to be something we could use as well. Thanks 
We are back with problems on Mandrill, which is weird because we checked all we could think it is the problem.

The error we have now is: "Email Sending Failed - SMTP Error: Could not authenticate."

Any suggestions on how to fix this?

- Henrique


New Member
Verified Provider
Perhaps contact their support to help you narrow down the issue. 

I have never had any technical issues with the service as its extremely stable and straight forward.


New Member
If you are using the api key as the password, have port 587 opened and are not using IP restrictions on the api it should work. If you are using api IP restrictions make sure you are using the IP that sends email. For us it was our root IP not our dedicated IP

Edit: restart your firewall and see if it works. We had an issue with CSF once that caused this. After a reboot of the firewall the problem disappeared.
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Verified Provider
Maybe my question sounds strange, but why deliver using STMP > Mandrill? In this case you still deliver using STMP which they say have a lower uptime.


New Member
Verified Provider
I've been using Mandrill with WHMCS, as well as a bunch of other scripts and have had zero issues to far with delivering mail. At one point I did use Office 365 for the company email and tried using it to deliver the email from WHMCS but constantly had issues with WHMCS not being able to connect to the Office 365 SMTP server. Since switching to Mandrill for the outgoing email to ensure delivery to inbox's and not junk folders I have not had any issues.

A nice feature with Mandrill is being able to view the account reputation and delivery percentage of sent mail, helps make sure your emails get delivered.


New Member
Just had this authentication issue with WHMCS and Mandrill.
It turns out i had to log into my servers WHM panel, navigate to /security Center/SMTP Restrictions/ and simply disable it.

Sorry to revive this thread but i couldn't find anywhere that had the answer for me.


New Member
Verified Provider
Did you try sendgrid or mailjet? They are working better maildrill.

I am using mailjet, and it can will help you prevent spamming, because it requires address verification.