[Dovecot] Dovecot sieve and duplicate email subjects

[Benjamin Thomas]

Hi,

I'm running a small email server with the help of iRedMail.

I can manage sieve scripts from the Rouncube web interface or manually
inside the user's personal sieve folder.

I have an email account setup to receive automated tasks.

Some of these "alerts" occur too often and they have the same subject line,
but different senders.

This is the rule I am currently using:

##CODE START##
# rule:[AutoAlerts]
if anyof (

header :matches "Subject" "AutoAlert Type1*",

header :matches "Subject" "AutoAlert Type2*",
header :matches "Subject" "AutoAlert Type3*"

)

{
        fileinto "INBOX.AutoAlerts";
        stop;
}
##CODE END##

I was wondering if it's possible to gracefully handle duplicate subjects
lines (within a given time frame) with sieve filters ?

Ideally, I would like the first email of the day with subject ""AutoAlert
Type1..." to get moved to the subfolder given above. Subsequent "duplicate"
emails would then go into a "duplicate" subfolder.

Is this possible with sieve filters ? I could not find anything striking me
as obvious while reading the page http://wiki.dovecot.org/LDA/Sieve.

Thanks very much for your input.