Sometimes, you’ll see this error when trying to add an new article, there is the error.

Error: DNNArticle Edit is currently unavailable. DotNetNuke.Services.Exceptions.ModuleLoadException: This property cannot be set to an empty string. Parameter name: value ---> System.ArgumentException: This property cannot be set to an empty string. Parameter name: value at System.Net.Mail.SmtpClient.set_Host(String value) at DotNetNuke.Services.Mail.Mail.SendMailInternal(MailMessage mailMessage, String subject, String body, MailPriority priority, MailFormat bodyFormat, Encoding bodyEncoding, IEnumerable`1 attachments, String smtpServer, String smtpAuthentication, String smtpUsername, String smtpPassword, Boolean smtpEnableSSL) at DotNetNuke.Services.Mail.Mail.SendMail(String mailFrom, String mailTo, String cc, String bcc, String replyTo, MailPriority priority, String subject, MailFormat bodyFormat, Encoding bodyEncoding, String body, List`1 attachments, String smtpServer, String smtpAuthentication, String smtpUsername, String smtpPassword, Boolean smtpEnableSSL) at DotNetNuke.Services.Mail.Mail.SendMail(String mailFrom, String mailTo, String cc, String bcc, String replyTo, MailPriority priority, String subject, MailFormat bodyFormat, Encoding bodyEncoding, String body, String[] attachments, String smtpServer, String smtpAuthentication, String smtpUsername, String smtpPassword, Boolean smtpEnableSSL) at DotNetNuke.Services.Mail.Mail.SendMail(String mailFrom, String mailTo, String cc, String bcc, MailPriority priority, String subject, MailFormat bodyFormat, Encoding bodyEncoding, String body, String attachment, String smtpServer, String smtpAuthentication, String smtpUsername, String smtpPassword, Boolean smtpEnableSSL) at DotNetNuke.Services.Mail.Mail.SendMail(String mailFrom, String mailTo, String cc, String bcc, MailPriority priority, String subject, MailFormat bodyFormat, Encoding bodyEncoding, String body, String attachment, String smtpServer, String smtpAuthentication, String smtpUsername, String smtpPassword) at ZLDNN.Modules.DNNArticle.PubEditor.SendEmail(DNNArticleInfo objDNNArticle, Boolean NewArticle, Boolean JustApproved, PortalSettings PortalSettings, Hashtable Settings, Boolean IsSendEmail, String Email, String EmailSubject, String EmailTemplate, String NewArticleEmailSubject, String NewArticleEmailTemplate, String ApprovedArticleEmailSubject, String ApprovedArticleEmailTemplate, Int32 SubscribeModule, String SubscribeEmailSubject, String SubscribeEmailTemplate) at ZLDNN.Modules.DNNArticle.BaseEditor.SendEmail(DNNArticleInfo objDNNArticle, Boolean NewArticle, Boolean JustApproved) at ZLDNN.Modules.DNNArticle.EditDNNArticle.SaveArticle() at ZLDNN.Modules.DNNArticle.EditDNNArticle.cmdUpdate_Click(Object sender, EventArgs e) --- End of inner exception stack trace ---

The issue is caused by new send email API in DNN 6.2. If the SMTP server is not set up, when the send email API is called, it will throw the error. To fix it is simple, you can set up the SMTP server in host->host settings. Or you can disable the email notification in module settings. It will solve your problem.