today a rather strange problem occured:
I tried to send two mails with less than 1s difference in time; while the first got sent correctly, the second didn't receive, I ended up with the following exception:
"One or more recipients rejected. Call SmtpException.GetRejectedRecipients() to get a collection of rejected email addresses.”
Is time an issue here? Do I need to wait between a sending period? If yes, how could I implement a valid routine to allow the correct sending process of both mails.