Getting the above prompt when i send email to some customer and vendor
Is like email keep bouncing back
Wierd was not all customer and vendor email that i forward to will encounter the above
Run malware, AV and even reinstall OS but still getting the above prompt
My webhost have request me to ask vendor to add smtp at their end but problem still persist
This DSN should be sent back by the sender SMTP server. The sender SMTP server is that server that your email client is using to send out email. It will be connecting to the receiver SMTP server. What you are getting is a notification from your sender SMTP server that it has repeatedly tried to send to the receiver SMTP server, but for whatever reason, it is not able to complete the delivery and then this mail is being enqueue back into the mail queue. The next time it was attempted again (maybe after several times) it was successfully sent, but it is already delayed.
There could be various reasons from receiver smtp server is heavily loaded, or offline, or misconfigured or have certain anti spam feature known as grey listing which is not accepting the mail and requested the sender SMTP to try again later.
