www.whitepeaksoftware.com/smtp-diagnostics

SMTP Diagnostics is a simple mail program enabling you to troubleshoot problems with outgoing email and assist with configuring outgoing (SMTP) servers.

An excellent SMTP diagnositc program with server response messages.

www.socketlabs.com/smtp-server-connection-diagnostics-tool/

Free SMTP Server Connection Diagnostics Tool enables you to connect to SMTP Servers and step through transactions with our without SSL.

www.arclab.com/en/amlc/

MailList Controller is an email newsletter software for sending personalized email marketing campaigns and newsletters to your contact lists.

This software has an extensive list of features.