SMTP Error 550 : Relaying Denied

How can I configure to treat an SMTP error 550 (Relaying denied) on outbound mail as a temporary failure so the message can be retried later?

My ISP uses "POP before SMTP" authentication and I make sure the POP3 box is checked before allowing Exim to send any mail but SOMETIMES the authentication seems to fail and I get VERY sporadic "550 Relaying denied" errors (one or two every few weeks). I've complained to the ISP about this problem but they haven't been able to fix it (even occurs using Windows Outlook Express!).

Because correctly processes these as permanent errors, my users get delivery failure notifications and I must try to explain the problem and
then ask them to re-send the messages (pretty embarassing!).

Is there any way to have an SMTP error 550 as if it were a
temporary error?

If you are at work or away from home and not using your ISP to connect to the Internet, and you want to send a message from your home ISP e-mail account, you must change your e-mail account settings to specify the SMTP server used at your location, for example, your work SMTP server.

What you can do is, making sure with your email administrator that your email server is setup to allow smtp relaying from trusted local internal IP addresses. Some email servers allow smtp relaying only if you log in and check email within the last 1 hour/day etc... In this case, you should use the pop3 authentication method to send email.

Hi,

You need to use a password to access your POP3 (incoming) server for your e-mail messages, this option requires that you provide a user name and password to send e-mail messages through the SMTP server. Usually, these are the same user name and password used for the POP3 server; however, they can be unique.