It is exactly what Jeff say.
You are confused cause the "user" word may be not-well understood, you need to make clean two different kind of user
First is USERNAME of the DA ACCOUNT, the second is the USERNAME of the email account (the part before @domain.tld)
Make for example that main username is MAX and his domain is MAXDOMAIN.tld
so, lets set a limit for the entire user MAX
echo "500" > /etc/virtual/limit_max
Now, lets say that MAX user have
[email protected] email and you wanna limit this email to 50:
echo "50" > /etc/virtual/maxdomain.tld/limit/info
As you can see, the single email value is LOWER than the user value, if i had put 5000 instead of 50, that value was invalid and the limit was set to 500 cause user MAX limit is 500.
Also, keep in mind that once you set a limit for a user (or a general limit), you can set a limit for each email account directly from DA web interface that MUST be lower than the main limit itself.
Also notice, that if you dont set a limit for the user account, than you can directly limit the single emails account, but keep in mind that set an email to 0 will be set as "no limit", and that's pretty insecure.
Regards