Create a key to copy examples filled with your team.
Send emails with SMTP
STARTTLS on port 587 with AUTH PLAIN.
Submit with STARTTLS on port 587. Use AUTH PLAIN. AUTH LOGIN does not work. The username looks like smtp_…. The REST API returns the password when it creates the credential; authorized dashboard users can reveal the encrypted value again. MAIL FROM must be a verified domain.
Set X-Capsule-Unique-Args to a JSON object. We strip it from the sent mail and put those keys on every delivery webhook. X-SMTPAPI unique_args works the same way.
send.sh
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swaks --server smtp.postshiba.com:587 --tls \
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--auth PLAIN --auth-user smtp_9 --auth-password YOUR_PASSWORD \
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--from hello@mail.example.com --to you@example.com \
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--header "Subject: PostShiba test" \
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--header 'X-Capsule-Unique-Args: {"campaign_id":"cmp_123","site":"docs"}' \
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--body "hello from PostShiba"