apenas por diversão eu tentei e funciona:
$ swaks -t [email protected] -s smtp.gmail.com:587 -tls -a LOGIN [enter]
Username: my.gmail.login
Password: my.password [password will be visible here, no asteriks]
=== 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:<[email protected]>
<~ 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: [email protected]
~> 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.
