Sunday, May 29, 2011

The mail server at "" rejected the sender's address

I’ve seen the situation a number of times where a client sends an email to a customer where the receiving email server rejects the message. In this case the receiving service is Hotmail.

The mail server at "" rejected the sender's address, <[email address removed]>.  This is a permanent error. "" said, "550 SC-001 Unfortunately, messages from weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to".

In the past when this has happened I’ve suggested the client contact the customer and ask them for an alternate email address. Another solution is to send the email using a different service provider.

The problem is companies like Hotmail/Microsoft are huge and they’ve probably identified spam or malware being sent from an internet address (IP) which the company sending the email is using and has no control over the IP address. The company isn’t doing anything wrong. The problem is when you send an email it has to go through your ISP. It is this ISP that is being blocked. One the ISP’s customers is probably sending spam or malware and the person sending the email is seen perhaps in the same range, or using the same dynamically assigned IP address.

The person who should receive the email thinks everything is OK on their end. The problem is Microsoft is blocking what the person can receive without their knowledge. I’ve seen this happen a number of times. I’d suggest a good way to fix this problem is to stop using Hotmail, or any other service that uses such a broad brush approach to blocking unwanted emails. Yes no one wants unwanted emails, but to block valid emails is just bad business practice and can lose companies business.

This is one reason I suggest that clients don’t use Hotmail for their business. If a potential customer sent you an email and it bounced you’d lose the business. I’m hoping that Microsoft does not apply the same level of rules to their upcoming Office 365 service or I’ll have to recommend clients not to use that service either. Given there is no way for me to know what Microsoft will do, it does make me now more cautious as to recommending Microsoft services.

In the past one approach clients have used is to simply wait for a few days and send the email again. With blocking it is sometimes done for a set period of time to stop and particular activity. In this instance the email worked perfectly yesterday but doesn’t work today. It is anyone’s guess if it will work tomorrow, but it is worth giving it a go. If it becomes a permanent problem you’ll need to look for a more permanent solution. It is a good backup plan to have a second ISP such as a mobile service provider or a web mail service provider to around this type of problem.


Kelvin Eldridge

No comments:

Post a comment