Passbolt doing a massive number of DNS MX Queries

Hi everyone !

Couldn’t find where to open issues on the GitHub so I’m posting here.

I have a pretty fresh Passbolt installation (Using Docker) and my server’s DNS request are all filtered through AdguardHome. Today I noticed that Passbolt was doing a insane amount of MX queries to the DNS (My Adguard), regarding the email domain we use at our company.

Adguard logged more than 8000 DNS requests in only 24 hours.

This wouldn’t be an issue if I had many users using the service all day, what makes it odd is that I don’t have any user registered yet and I haven’t used the service yet today. So Passbolt is making hundreds of DNS request autonomously for no apparent reason. Perhaps it serves a purpose (But I doubt it is necessary to make this much traffic), but I’d rather think that there is a issue in the codebase somewhere.

Let me if you guys notice that too in your installation.


This is most likely due to the email validation function that has an option to validate the domain, e.g. check if the domain exist for real. Do you have the PASSBOLT_EMAIL_VALIDATE_MX flag set to enabled by any chance?


Hi, yes I have this option enabled. But still, I fell like it shouldn’t make DNS requests 5 times per seconds.