Syntactically invalid HELO argument(s)

[szkodnik25]

Hello,
I'm developing app for Android and WP 8.1 which will be sending emails in background. For Android I used JavaMail API and it worked. For WP i wanted to use MailKit, but with the same credentials I used in Android (on port 587) i get the following exception during client.Connect(...):

MailKit.Net.Smtp.SmtpCommandException: Syntactically invalid HELO argument(s)
at MailKit.Net.Smtp.SmtpClient.Ehlo(CancellationToken cancellationToken)
at MailKit.Net.Smtp.SmtpClient.Connect(String host, Int32 port, SecureSocketOptions options, CancellationToken cancellationToken)

What can cause this exception?
Best regards,
Matthew

[jstedfast]

I don't know, you'll have to attach a protocol log (see the FAQ for how to get one).

In the worst case, you can set the LocalDomain property of the SmtpClient to override the argument sent in the HELO command.

Most likely either the server is broken (e.g. it's not accepting an IP address like it's supposed to) or else a DNS lookup of your machine's IP address is giving back some bogus illegal string that the SMTP server won't accept.

[szkodnik25]

Thank you for your answer.

Here is protocol log:

Connected to smtp://smtp.da16.domeny.com:587/?starttls=always
S: 220 db16.domeny.com ESMTP Wed, 08 Jun 2016 13:29:52 +0200
C: EHLO [Windows.Networking.Connectivity.IPInformation]
S: 501 Syntactically invalid EHLO argument(s)
C: HELO [Windows.Networking.Connectivity.IPInformation]
S: 501 Syntactically invalid HELO argument(s)

[jstedfast]

This should be fixed now if you clone the source code from github

[jstedfast]

I have published a new version of MailKit that fixes this issue to nuget.

[szkodnik25]

Thanks, I will take a look soon.