sendEmail is described as 'lightweight, command line SMTP email client. If you have the need to send email from a command line, this free program is perfect: simple to use and feature rich' and is an app in the OS & Utilities category. There are eight alternatives to sendEmail for Windows, Linux, BSD, Xfce and Mac. The best alternative is mailsend-go, which is both free and Open Source. Other great apps like sendEmail are msmtp (Free, Open Source), sSMTP (Free, Open Source), blat (Free, Open Source) and Mailer (Free).
mailsend-go is a command line tool to send mail via SMTP protocol. This is the golang incarnation of the C version of mailsend. However, this version is much simpler and all the heavy lifting is done by the package gomail.
sSMTP is a simple MTA to deliver mail from a computer to a mail server. sSMTP is simple and lightweight, there are no daemons or anything hogging up CPU; Just sSMTP. Unlike Exim4, sSMTP does not receive mail, expand aliases, or manage a queue.
Blat is a small, efficent SMTP command line mailer for Windows. It is the SMTP *sending* part of an eMail User Agent (MUA) or eMail client. As such, Blat sends eMail via SMTP (or internet eMail) from the command line, or CGI.
Free utility to send emails from the command line. No Installation. All contained in one file. MIME detection based on file extension. Multiple recipients (to/cc/bcc). SMTP SSL/TLS support. SMTP Authentication (clear). Environment variable support.
CMail is a command line mailer, originally developed for testing mail server software, but is simple enough to use interactively. CMail supports IPv6, TLS/SSL, authentication, multiple message body and attachment encoding methods, and mail delivery via proxies.
esmtp is a user configurable relay-only Mail Transfer Agent (MTA) with a sendmail compatible syntax. It's based on libESMTP supporting the AUTH (including the CRAM-MD5 and NTLM SASL mechanisms) and the StartTLS SMTP extensions.
You can send the mails via an smtp server, such as blat, supports authentication and ssl. In addition, he can also send emails via the OWA interface (i.e. the Exchange Server can also be used for external sending if the OWA is published).