102 - Unable to resolved the SMTP server hostname - Connection Lost


I’m hoping someone might know why one of my customers is getting this error when sending emails - “102 - Unable to resolved the SMTP server hostname - Connection Lost”. I am using an SMTPSecureSocket to send emails and it worked up to recently without issue, but now the customer could try to send the email up to 4 times before the email is sent without an error. My other customers are not experiencing the same issue and the customer is question is able to send emails to the same email addresses through Outlook without an issue. The customer is using Microsoft Exchange. Thanks for any help


See if they have IPv6 enabled but have an unresponsive or non-existent IPv6 dns server set up on the connection which ultimately fails back to their IPv4 connection and starts working.

I recently had this which was causing xojo’s language reference to fail because is was performing an nslookup as a network check which was going over a failed IPv6 connection instead of my perfectly working IPv4 route to the internet.

It might be related, it might not, but it’s something that came to mind.

Thanks very much Julian for your reply. I understand IPv6 is disabled, but I’ll double-check to make sure. I presume with it disabled, your issue wouldn’t occur?


I had exactly this issue, but using Microsoft public services. A client have an user that had an user@live.com address that started to fail with 102 connection lost; and the fix was him to change the smtp settings in my app to smtp.office365.com , port 587, STARTTLS, TLSv1.2

Thanks very much Rick. I’ll try change to those settings and see how it goes.

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Sorted! Thanks very much again Rick!

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