[exim] Absent username and "Failed to get user name for uid"

Hello.

I've some php scripts which start by uid without username and send
mails. (It's not a spam.)

exim panic and say "Failed to get user name for uid 2045 ..."
Yes, the uid has not a user name in /etc/passwd.

Can I set user names for my uids to exim wo change system /etc/passwd
(some lookup from text file etc.) or set one default username to all
my special uids for exim?

Thanks,

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=== Henry Pootel ===