Sat, 09 Sep 2006
Denisa decided she doesn't want to feel compelled to check her email all day
long, and asked me if there was a way to restrict the hours during which she
could receive email. Since I use the magical MTA that is Exim, I was sure this
must be possible. While I couldn't find explicit support for such a feature, I
was able to hack something out. Here's my new local_delivery transport:
local_delivery:
driver = appendfile
envelope_to_add
file = /var/spool/mail/${local_part}
group = mail
mode = 0660
no_mode_fail_narrower
return_path_add
# hack to queue messages during certain hours
message_size_limit = ${if ! and {\
{match_local_part{$local_part}{+time_restricted_users}} \
{or {{<{${substr_11_2:$tod_log}}{21}}{>={${substr_11_2:$tod_log}}{22}}}} \
}{0}fail}
The trick I used was to force expansion failure of the message_size_limit when
delivering a message to her address and when the current time matches our
constraints, in this case before 9pm or after 10pm. The expansion failure
causes the message to be queued. To ensure that she actually gets her queued
messages during that one hour window, I added a new retry rule for our domain
that retries every 15 minutes for four days, rather than the default rule which
increases the interval between delivery attempts as the time on the queue
increases. In case I ever want to configure other accounts similarly, I set up
a localpartlist named time_restricted_users.
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