Suggestion: Support 'TLS optional' usage about aiosmtplib

[gurnec]

FYI for just STARTTLS you can use something like this to avoid reconnecting:

async with SMTP(hostip, source_address=local_fqdn) as client:
    try:
        await client.starttls(validate_certs=False)  # opportunistic TLS
    except SMTPException as exc:
        if 'starttls extension not supported' not in exc.message.lower():
            raise
    return await client.send_message(message)

For SMTP over TLS, I don't think there's any alternative but to try and catch (even if it were implemented by aiosmtplib, internally it would have to do the same thing).

[cole]

The newest beta (v2.0.0b0) improves this situation slightly by checking for STARTTLS support and upgrading the connection automatically if it's present by default.

The TLS on connect situation isn't really improved though. The lower level connect APIs don't really make it easy to handle TLS connections transparently, unfortunately.

[cole]

Closing as partially fixed