$ swaks -t user@domain.tld -s smtp.gmail.com:587 -tls -a LOGIN
Username: my.gmail.login
Password: my.password
=== Trying smtp.gmail.com:587...
=== Connected to smtp.gmail.com.
<-  220 smtp.gmail.com ESMTP a45sm2396859eda.3 - gsmtp
 -> EHLO e7250
<-  250-smtp.gmail.com at your service, [77.249.1.91]
<-  250-SIZE 35882577
<-  250-8BITMIME
<-  250-STARTTLS
<-  250-ENHANCEDSTATUSCODES
<-  250-PIPELINING
<-  250-CHUNKING
<-  250 SMTPUTF8
 -> STARTTLS
<-  220 2.0.0 Ready to start TLS
=== TLS started with cipher TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128
=== TLS no local certificate set
=== TLS peer DN="/C=US/ST=California/L=Mountain View/O=Google Inc/CN=smtp.gmail.com"
 ~> EHLO e7250
<~  250-smtp.gmail.com at your service, [77.249.1.91]
<~  250-SIZE 35882577
<~  250-8BITMIME
<~  250-AUTH LOGIN PLAIN XOAUTH2 PLAIN-CLIENTTOKEN OAUTHBEARER XOAUTH
<~  250-ENHANCEDSTATUSCODES
<~  250-PIPELINING
<~  250-CHUNKING
<~  250 SMTPUTF8
 ~> AUTH LOGIN
<~  334 xxxxxxxxxxx
 ~> xxxxxxxxxxxxxxx
<~  334 xxxxxxxxxxxxxxx
 ~> xxxxxxxxxxxxxxxxxxxxxxxxxxxx==
<~  235 2.7.0 Accepted
 ~> MAIL FROM:<user@host>
<~  250 2.1.0 OK a45sm2396859eda.3 - gsmtp
 ~> RCPT TO:<user@domain.tld>
<~  250 2.1.5 OK a45sm2396859eda.3 - gsmtp
 ~> DATA
<~  354  Go ahead a45sm2396859eda.3 - gsmtp
 ~> Date: Sun, 23 Apr 2017 10:35:17 +0200
 ~> To: user@domain.tld
 ~> From: user@host
 ~> Subject: test Sun, 23 Apr 2017 10:35:17 +0200
 ~> X-Mailer: swaks v20130209.0 jetmore.org/john/code/swaks/
 ~>
 ~> This is a test mailing
 ~>
 ~> .
<~  250 2.0.0 OK 1492936526 a45sm2396859eda.3 - gsmtp
 ~> QUIT
<~  221 2.0.0 closing connection a45sm2396859eda.3 - gsmtp
=== Connection closed with remote host.