[exim] problems using altermime with exim

Hello All,

We've following exim configuration for adding "disclaimer" to outgoing emails based on certain domain.

In Router's section we've:

disclaimer:
debug_print = "R: dnslookup_withdisclaimer for $local_part@$domain"
driver = dnslookup
transport = disclaimer_smtp
condition = ${if exists {/home/${lookup{$sender_address_domain}lsearch* {/etc/userdomains}{$value}}/htmldisclaimer}{true}{false}}


In transports section we've:

driver = smtp
#user = "${lookup{$sender_address_domain}lsearch{/etc/userdomains}{$value}}"
transport_filter = /usr/bin/altermime --input=- --disclaimer=/home/${lookup{$sender_address_domain}lsearch{/etc/userdomains}}/textdisclaimer --disclaimer-html=/home/${lookup{$sender_address_domain}lsearch{/etc/userdomains}}/htmldisclaimer
size_addition = -1

For some reason, on certain domains when used with distribution list (mailman) email are going out with junk content.
Does anybody has similar experience ?
Appreciate if anyone can help what is wrong with above configuration and why sometimes email content is going junk.

Thanks
Rajesh