Upgrade broke smtp

We just upgraded from 2018.x.x to 2021.1 and while most things appear to be working fine we now get an error when trying to send emails through octopus.

I have attached a screenshot of the error:

Is this a know issue? As far as i know we have TLS 1.2 enabled on the smtp server. However we don’t tick the box for “Use SSL/TLS” and we connect on port 25. None of this has changed from pre upgrade. We have tested with different ports and ticked/unticked the TLS/SSL box but it’s not connected at any point.

Hi Adam,

Thank you for reaching out to us with your query.

We use the MailKit library for SMTP and there have been updates made to it between those two releases. It is possible that the updated library is handling TLS differently and uncovering a configuration issue with your SMTP server that was previously ignored.

The issue appears to be that your SMTP server is offering TLS support but then failing to actually allow it to work. It’s worth noting that Octopus will attempt to use TLS if the server supports it regardless of the “Use SSL/TLS” setting (the setting forces SSL/TLS when active).

Could you please check that your SMTP server is configured correctly? One possible avenue to explore could be connecting using a standard mail client to see if the same issue is present and to verify which SSL/TLS connection options work and which do not.

Best Regards,


Thanks Charles, it was an SMTP issue and was resolved our side. Cheers for clearing it up.

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