This explains how to add info to outgoing e-mails about auto deletion of accounts.
It is language specific, however, the example is for English only.

When editing the .tpl files, you do not have to insert the {DELETION_INFO} var
where I have it.  You may, in fact, put it anywhere you so desire on that
page you are editing.

# 
#-----[ OPEN ]------------------------------------------ 
# 
language/lang_english/email/user_welcome.tpl

# 
#-----[ FIND ]------------------------------------------ 
#
Thank you for registering.

# 
#-----[ BEFORE, ADD ]------------------------------------------ 
#
{DELETION_INFO_NON_POSTING}
{DELETION_INFO_NON_VISITING}

# 
#-----[ OPEN ]------------------------------------------ 
# 
language/lang_english/email/user_welcome_inactive.tpl

# 
#-----[ FIND ]------------------------------------------ 
#
Thank you for registering.

# 
#-----[ BEFORE, ADD ]------------------------------------------ 
#
{DELETION_INFO_NON_POSTING}
{DELETION_INFO_NON_VISITING}
{DELETION_INFO_INACTIVE}

# 
#-----[ OPEN ]------------------------------------------ 
# 
language/lang_english/email/user_activate.tpl

# 
#-----[ FIND ]------------------------------------------ 
#
{EMAIL_SIG}

# 
#-----[ BEFORE, ADD ]------------------------------------------ 
#
{DELETION_INFO_NON_POSTING}
{DELETION_INFO_NON_VISITING}
{DELETION_INFO_INACTIVE}

# 
#-----[ OPEN ]------------------------------------------ 
# 
includes/usercp_register.php

# 
#-----[ FIND ]------------------------------------------ 
#
// ---------------------------------------
// Load agreement template since user has not yet
// agreed to registration conditions/coppa
//

# 
#-----[ BEFORE, ADD ]------------------------------------------ 
#
include ($phpbb_root_path . 'includes/functions_admin_auto_delete_users.php');
load_auto_delete_emailer_info();

# 
#-----[ SAVE & CLOSE ALL FILES ]-------------------------- 
# 
#End 