id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
2159	Massmail problems with mail module	mmgit@…		"We encountered a problem when sending mass-mails thru NGINX. When sending a mail to more than (in our case) ~130 recipients, NGINX closes the connection during the SMTP connection without an error.

What we found is, that this error only occurs when TLS and pipelining is involved. If either TLS or pipelining is deactivated, sending the mail works.
Another workaround is to increase the smtp_client_buffer. On our test system the mempage size is 4k.

What we saw in a capture is that when we send a mail with 130 recipients and pipelining is activated, NGINX receives the recipient commands and accepts them with 250 2.0.0 OK but then closes the TCP connection with a FIN.
I think it would be better that the sender gets an error if there is a to small buffer size."	defect	closed	minor		nginx-module	1.18.x	fixed	smtp,mail		Linux mailtest01 4.19.0-16-amd64 #1 SMP Debian 4.19.181-1 (2021-03-19) x86_64 GNU/Linux	"nginx version: nginx/1.18.0
built by gcc 8.3.0 (Debian 8.3.0-6) 
built with OpenSSL 1.1.1d  10 Sep 2019
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --modules-path=/usr/lib/nginx/modules --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --pid-path=/var/run/nginx.pid --lock-path=/var/run/nginx.lock --http-client-body-temp-path=/var/cache/nginx/client_temp --http-proxy-temp-path=/var/cache/nginx/proxy_temp --http-fastcgi-temp-path=/var/cache/nginx/fastcgi_temp --http-uwsgi-temp-path=/var/cache/nginx/uwsgi_temp --http-scgi-temp-path=/var/cache/nginx/scgi_temp --user=nginx --group=nginx --with-compat --with-file-aio --with-threads --with-http_addition_module --with-http_auth_request_module --with-http_dav_module --with-http_flv_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_mp4_module --with-http_random_index_module --with-http_realip_module --with-http_secure_link_module --with-http_slice_module --with-http_ssl_module --with-http_stub_status_module --with-http_sub_module --with-http_v2_module --with-mail --with-mail_ssl_module --with-stream --with-stream_realip_module --with-stream_ssl_module --with-stream_ssl_preread_module --with-cc-opt='-g -O2 -fdebug-prefix-map=/data/builder/debuild/nginx-1.18.0/debian/debuild-base/nginx-1.18.0=. -fstack-protector-strong -Wformat -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fPIC' --with-ld-opt='-Wl,-z,relro -Wl,-z,now -Wl,--as-needed -pie'"