Domain wide footer: enabling it causes extra blank line at beginning of text/plain message body

[ralfbergs]

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Description

I enabled "Domain wide footer" for my test domain. When I send a plain-text-only message, there's now suddenly an extra blank line at the *beginning* of the message body.

It seems that when "mangling" the message to add the footer, this extra line is introduced into the message body.

Logs:

Not helpful.

Steps to reproduce:

1. Enable "Domain wide footer" for a domain.
2. Use a single line as the "plain" footer for testing. I did not use a trailing line break, dunno if it matters.
3. (MUA doesn't matter) Send plain-text email from one mailbox in that domain, containing just a single word "Test", with no blank line before it.
4. (On the receiving end:) Note that there is now a single blank line on top of the line "Test".

Which branch are you using?

master

Which architecture are you using?

x86

Operating System:

Debian 12.7

Server/VM specifications:

AWS m5.large: 8 GB RAM, 2 vcores

Is Apparmor, SELinux or similar active?

no

Virtualization technology:

AWS EC2

Docker version:

27.3.1

docker-compose version or docker compose version:

v2.29.7

mailcow version:

2024-08a

Reverse proxy:

none

Logs of git diff:

[TLS key pair omitted]

diff --git a/data/conf/postfix/main.cf b/data/conf/postfix/main.cf
index 6a87f2ec..d7ed4beb 100644
--- a/data/conf/postfix/main.cf
+++ b/data/conf/postfix/main.cf
@@ -173,3 +173,31 @@ parent_domain_matches_subdomains = debug_peer_list,fast_flush_domains,mynetworks

 # DO NOT EDIT ANYTHING BELOW #
 # Overrides #
+
+postscreen_dnsbl_sites = wl.mailspike.net=127.0.0.[18;19;20]*-2
+  hostkarma.junkemailfilter.com=127.0.0.1*-2
+  list.dnswl.org=127.0.[0..255].0*-2
+  list.dnswl.org=127.0.[0..255].1*-4
+  list.dnswl.org=127.0.[0..255].2*-6
+  list.dnswl.org=127.0.[0..255].3*-8
+  ix.dnsbl.manitu.net*2
+  bl.spamcop.net*2
+  bl.suomispam.net*2
+  hostkarma.junkemailfilter.com=127.0.0.2*3
+  hostkarma.junkemailfilter.com=127.0.0.4*2
+  hostkarma.junkemailfilter.com=127.0.1.2*1
+  backscatter.spameatingmonkey.net*2
+  bl.ipv6.spameatingmonkey.net*2
+  bl.spameatingmonkey.net*2
+  b.barracudacentral.org=127.0.0.2*7
+  bl.mailspike.net=127.0.0.2*5
+  bl.mailspike.net=127.0.0.[10;11;12]*4
+  [REDACTED].zen.dq.spamhaus.net=127.0.0.[4..7]*6
+  [REDACTED].zen.dq.spamhaus.net=127.0.0.[10;11]*8
+  [REDACTED].zen.dq.spamhaus.net=127.0.0.3*4
+  [REDACTED].zen.dq.spamhaus.net=127.0.0.2*3
+postscreen_dnsbl_reply_map = texthash:/opt/postfix/conf/dnsbl_reply.map
+
+# User Overrides
+myhostname = [REDACTED]
+

Logs of iptables -L -vn:

Doesn't matter

Logs of ip6tables -L -vn:

Doesn't matter

Logs of iptables -L -vn -t nat:

Doesn't matter

Logs of ip6tables -L -vn -t nat:

Doesn't matter

DNS check:

104.18.32.7
172.64.155.249