Hello, I am having a weird issue with libesmtp : it does not use TLS, confirmed by wireshark sniffing. The ASP repo was pulled, and here is the result of ./configure --prefix=/usr : ************************* *** libESMTP features *** ************************* --with-auth-plugin-dir: /usr/lib/esmtp-plugins --with-lwres: no --with-openssl: no --enable-pthreads: yes --enable-etrn: no --enable-ntlm: no --enable-chunking: yes --enable-xusr: yes --enable-nsauth: yes --enable-debug: no After examining config.log, the conftest.c program, generated by configure, failed to compile : #ifdef __cplusplus extern "C" #endif char SSL_library_init (); int main () { return SSL_library_init (); ; return 0; } By including <openssl/ssl.h> before int main(), conftest.c does compile. Talking to an SMTP server without TLS is obviously not an option. How can this be fixed ? A patch by the package maintainer ? Reporting to upstream ? (Seems to be fedora here) Regards.