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Date: Sat, 5 Jan 2019 20:54:21 -0800 (PST)
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Subject: 530 5.7.0 Must issue a STARTTLS command first.
From: Andrew Shvets <andrew.shvets@gmail.com>
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Xref: reader01.eternal-september.org comp.lang.ada:55208
Date: 2019-01-05T20:54:21-08:00
List-Id: <comp.lang.ada>

I've looked through this group and taken the advice that was recommended in regards to sending e-mails using Ada and decided to try something very simple.  On RosettaCode, there is the following example:
http://rosettacode.org/wiki/Send_email#Ada

When I run the code configured for my Gmail account (smtp.gmail.com and port being 587), I get the below error:
530 5.7.0 Must issue a STARTTLS command first. 126sm25673591qkj.70 - gsmtp

Why is that?  And how can I send a STARTTLS command first?