Bug report: Pigeonhole Sieve delivery plugin fail s to load in Dovecot 2.4 — undefined symbol mail_deliver_ctx_get_log_var_expand_tabl e

Hello Dovecot Team,

I am reporting what appears to be a packaging/ABI issue affecting the 
Pigeonhole Sieve delivery plugin in Dovecot 2.4. I have performed 
extensive diagnostics and would appreciate any guidance.

Environment
Operating System: Debian 13 (Trixie), amd64
Repository: Official Dovecot CE repository 
(repo.dovecot.org/ce-2.4-latest/debian/trixie)
Installed package version:2:2.4.4-5+debian13
Installed packages:

dovecot-core
dovecot-sieve
dovecot-lmtpd
dovecot-imapd
dovecot-pop3d
dovecot-managesieved
dovecot-pgsql
All packages are installed at the exact same version.

Problem Description
When enabling the Sieve delivery plugin with:

mail_plugins {
   sieve = yes
}
Dovecot fails to load the plugin with the following error:

sievec: Fatal: Couldn't load required plugin /usr/lib/dovecot/modules/lib90_sieve_plugin.so:
dlopen() failed: /usr/lib/dovecot/modules/lib90_sieve_plugin.so:
undefined symbol: mail_deliver_ctx_get_log_var_expand_table
As a result, message delivery fails entirely whenever the Sieve delivery 
plugin is enabled. Disabling the plugin restores normal mail delivery.

Diagnostics Performed1. Package verification
All installed packages are version 2:2.4.4-5+debian13 from the official 
Dovecot CE repository. There are no mixed package versions.

2. Symbol verification
I searched for the symbol mail_deliver_ctx_get_log_var_expand_table 
throughout the Dovecot libraries.

Results:

nm -D on libdovecot-lda.so.0.0.0 → symbol not found

readelf -sW on libdovecot-lda.so.0.0.0 → symbol not found

Recursive search across all .so files under:

/usr/lib/dovecot/
/usr/lib/x86_64-linux-gnu/dovecot/
→ symbol not exported anywhere
The symbol string exists inside both:

lib90_sieve_plugin.so
libdovecot-lda.so.0.0.0
but only as plain text (visible via grep), never as an exported ELF 
symbol.

3. Dependency verification
ldd on lib90_sieve_plugin.so shows dependencies on:

libdovecot-sieve.so.0
libdovecot-storage.so.0
libdovecot.so.0
It does not directly link against libdovecot-lda.so.

4. Standalone sievec
Compiling a Sieve script works correctly:

sievec /tmp/test.sieve
Exit status is 0 as long as no configuration enables the Sieve delivery 
plugin.

The failure only occurs once:

mail_plugins {
   sieve = yes
}
is present in the configuration.

Reproduced on a Clean Debian 13 Installation
To rule out configuration or upgrade issues, I reproduced the exact same 
problem on a completely clean debian:13-slim container.

I installed only the Debian stable packages:

apt-get install dovecot-core dovecot-sieve dovecot-lmtpd
(version 1:2.4.1+dfsg1-6+deb13u6)

Using the same production configuration with:

mail_plugins {
   sieve = yes
}
produces the exact same error:

sievec: Fatal: Couldn't load required plugin ...
undefined symbol: mail_deliver_ctx_get_log_var_expand_table
This indicates the problem is not caused by:

mixed package versions
an upgrade issue
local modifications
custom configuration
The issue reproduces consistently on both:

Dovecot CE 2.4.4
Debian 13's packaged Dovecot 2.4.1
Questions
Is mail_deliver_ctx_get_log_var_expand_table a new internal function 
that should be exported in Dovecot 2.4? Was there an ABI change 
affecting the Pigeonhole plugin?

Is this a known issue in the Dovecot 2.4.x packages? If so, is a fix 
planned (for example, in 2.4.5)?

Is there any recommended workaround for using Sieve during message 
delivery (e.g. moving spam to the Junk folder) while this issue is 
unresolved?

I am trying to use the new Dovecot 2.4 configuration syntax 
(sieve_script_type, sieve_script_precedence, and sieve_script_path), 
since sieve_before and the plugin {} block were removed in 2.4.

Thank you for your time. I would be happy to provide additional logs, 
the complete doveconf -n output, or a core dump if that would be 
helpful.

Best regards,

Miguel A Morales

Server: Debian 13 (amd64)
Dovecot: 2.4.4-5+debian13

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