As promised here is a working optimized version. The issue was syntax with the host as far as the nasty hang that would never segmentation fault. DO NOT PUT A :
What needs work is there is no flood control. I just drilled on the console and sent and received 10 e-mails in a few seconds.
telnet: could not resolve mail.gnu.org:25/telnet: Name or service not known
telnet mail.gnu.org 25
Connected to mail.gnu.org.
Escape character is '^]'.
220 eggs.gnu.org ESMTP Exim 4.71 Sun, 06 Oct 2019 15:46:16 -0400