Sending invoices by email error

Hi

Every time I go to send an invoice to a customer after I’ve created it, it comes up with the following error code:
Sales Quote - B & N Home & Garden Services - Manager ul, ol { padding-left: 10px }.float-left { float: left !important; }.float-right { float: right !important; }.text-align-left { text-align: left !important; }.text-align-right { text-align: right !important; }div.content { background-color: #fff; padding: 30px; box-shadow: 0px 0px 5px #ccc; border: 1px solid #ccc; width: auto }a.file-close:hover { color: #999; }#sidenav div { padding: 0px; background-color: #fafafa; box-shadow: inset 1px 1px 0px #fff; }#sidenav img { opacity: 0.4; vertical-align: top; width: 16px; height: 16px }#sidenav .tab-active { background-color: #fff; border-right: none }#sidenav a.tab-link, #sidenav span.tab-link { line-height: 16px; display: block; white-space: nowrap; padding: 12px; font-size: 11px; font-weight: bold; }#sidenav table { border: 1px solid #ccc; border-top: none; font-family: ‘Lucida Grande’,Verdana,sans-serif; border-spacing: 0px; width: 100% }#sidenav .tab-active table { border-right: 1px solid #fff }#sidenav a:hover { text-decoration: none }#sidenav a:hover img { opacity: 0.6 }#sidenav .tab-active img { opacity: 0.6 }#sidenav span.count { background-color: #FFFFFF; border: 1px solid #CCCCCC; border-radius: 3px 3px 3px 3px; color: #666666; font-size: 10px; font-weight: bold; padding: 3px 6px; }#sidenav span.count-zero { border: 1px solid #EEEEEE; color: #DDDDDD }#sidenav span.tab-label { margin-left: 10px; }@media print { body { -webkit-print-color-adjust: exact !important; } }

System.Net.Mail.SmtpException: System.Net.Mail.SmtpException: Syntax error, command unrecognized. The server response was: 5.7.0 Mailgun is not loving your login or password
at System.Net.Mail.RecipientCommand.CheckResponse(SmtpStatusCode statusCode, String response)
at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception)
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at ManagerServer.HttpHandlers.Businesses.Business.Email.Post()

What does this mean? Please help.

Thanks

basic details first.
what version?
what edition?
what OS?

have you read the guide https://www.manager.io/guides/10643 ?

Manager 17.6.37

Manager no longer includes an in-built smtp server. you need to use a custom smtp server.
you need to update Manager to the latest version and follow the guide linked above.

Part of the message shows that the “Mailgun SMTP server” does not like the username and password you have entered in Manager mail settings. Check that the information and port used are correct for the mailgun. Alternatively configure for gmail smtp services.