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31

Short Answer: You can't. For more info, this gives a basic explaination as to why. This shows how easy it is to do. It's just the nature of SMTP, it's insecure! Just because an email appears to come from somebody, it doesn't mean it did.


23

You could set up SPF records for your email domains, however this will only have a limited effect, if any.


15

As long as you bounce the mail by refusing to receive it in the first place, then a spammer cannot use you to annoy somebody innocent with a lot of bounces. You can either return an error on the RCPT TO command, which is what usually happens in case of a non-existent address, or you can return success on the RCPT TO command but return an error at the end of ...


12

Tech support is wrong. There is nothing you can do to stop someone else sending email as if it came from your account(s). Only the receiving system can do anything about it. Measures such as SPF, DKIM and the like help the receiving systems validate senders but such things are not a requirement by any standards and those systems which enforce such things are ...


8

To receive emails from other servers, you need to be listening on port 25. Port 587 is the submission port, intended for clients to submit mail for delivery. Other mail servers will never try to connect to this port.


8

Based on the information you've provided, this is almost certainly not coming from your server unless you run an open relay. The message originated in China: inetnum: 123.112.0.0 - 123.127.255.255 netname: UNICOM-BJ descr: China Unicom Beijing province network descr: China Unicom country: CN admin-c: ...


7

it should be immediately rejected. Senders mail server should inform the sender about failure with non-delivery report.


7

What I usually do is set up a mail forwarder as a backup MX - that is, a mail server that isn't the destination for any emails but can hold on to them (leave them on hold) in case something goes wrong. The upside to this is that the moment your main mail server goes back up the emails start being delivered as if nothing happened - you don't have multiple ...


7

Ubuntu-1004-lucid-64-minimal is not a valid global name, tell postfix to use your "real" domain name, using the myhostname setting: http://www.postfix.org/postconf.5.html#myhostname


6

The mail server mx.maxus.pl attempted to look up the domain name in the From: email address, aquarius@aquariusprams.co.uk, and was unable to find it. This means your recipient's mail server is having trouble resolving domain names correctly, as I was able to look this up successfully. The problem is with the recipient's mail system, not with your Google ...


6

I'm going to make this answer fairly generic because the terminology and configuration details will vary depending on your specific mail server/spam filter software. There are actually 3 approaches for an invalid recipient: After the recipient is determined to be invalid, send an Undeliverable message back to the sender. Close the SMTP connection while ...


5

Frankly the best way is not to do mass emails from anything remotely related to your domain. By definition anything unsolicited mass emailed is spam. If it's solicited then the recipients will whitelist it.


5

Have a look at the Powershell Dig Cmdlet. Using this you are able to do this: PS> $allRecords = Get-Dns -Name mydomain.com -Type MX PS> write-host $allRecords.RecordsMX $allRecords is of type PoshNet.Dns.Response so you can read the properties on it to get your records. Something else nice about this cmdlet is that you can have it return multiple ...


5

As others have said, you can't stop the spammer from using your address or do much to prevent the receiver from sending you a bounce. Those receiving servers are already misconfigured at least one way: they should have rejected the message without accepting it. That would make it the sender's job to produce a bounce, which the spam software is not going ...


5

Hand this responsibility over to somebody else. Postini, AppRiver, and Symantec are all examples of companies that do this for you. Let them filter your spam before it gets to your network and spool your email should your server go down. It's much better than putting together your own solution which could also go down (like if you have an extended internet ...


5

In the log you posted: Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. (in reply to MAIL FROM command)) The previous owner of your IP address sent junk mail from it, and Hotmail has banned it. Try putting your IP ...


5

The return path for bounces is determined by the envelope sender (the MAIL FROM line in the smtp protocol). In the mail headers this is generally copied to the Return-Path header. Here's an example of a mailing list mail that specifies bounces should go to the mailing list server instead of the sender of the mail: Return-Path: ...


4

If you are expecting your mail to be reliably delivered, then a soft fail is not good. Your message may still be delivered depending on the policy of the receiving system. For the best chance of successful delivery you should update your SPF record so the message you are trying to send is permitted.


4

Out-Of-Office replies do usually get sent via return-path, yes. It's correct to the RFC specs, too. More info here: http://tools.ietf.org/html/rfc3834


4

A hard bounce is an indication that you should never send a message to that address. The bounce message should contain an indication as to why you were bounced. If the address does not exist, then no amount of waiting is likely to resolve the issue. If you get a soft bounce, such as you should get for over quota, use an exponential backoff. This should ...


4

You can never be sure you'll not lose email. That's just not in the protocol. However, properly configured email servers will try again for something like 12 to 48 hours, with longer and longer windows between retry attempts rather than just dropping the email altogether. Technically you can't control what other mail servers do or if they're configured ...


4

Do I need to place that text in quotes ""? The missing quotes should be the problem indeed, as explained e.g. in Record Types Supported: Unlike with most other record types, for TXT records the Data field is essentially free-form and may even include spaces. Please note: When entering a string that includes spaces, such as SPF records, you must ...


4

Yes it is possible to send to mailbox@ip, if you want to strictly conform to the RFCs, then supporting this is required. But in this day and age it is extremely common for this to not be supported. If you want to strictly follow the RFCs you will have an abuse and postmaster accounts that are read by a human. But if you actually have these accounts and ...


4

Although technically this is a grey-area my own view on this is far more black and white. Ultimately you're running out of IPs because you're targetting emails to people who don't want them, they're complaining and thus the IPs are being removed from your options. There's no real technical way around this, other than moving email provider anyway but even ...


4

No. If you need to do this you will need a mail-aware application running on :25 on the servers that are the targets for the MX records that can sort out where to deliver or forward the mail to.


4

We got bounce message from 118.69.183.136. But why does it bounce to both manager1@gmail.com and manager2@gmail.com? Did they both send an email, which could not be delivered? Unlikely. It isn't bouncing to the two addresses, it's bouncing it to postmaster telling you that delivery to those two addresses failed. Then google replies with "421-4.7.0 ...


4

Accoding to the answers given at http://stackoverflow.com/questions/386294/what-is-the-maximum-length-of-a-valid-email-address The answer is 254 according to RFC 5321 So, those MTA are badly configured.


4

Email is not instant messaging; it is email. Let me explain. Masegaloeh is correct with regard to assumptions, but there is one other explanation that you have overlooked: email is queued. Just because a message is accepted for delivery, doesn't mean that it has been delivered. And that's just the beginning. The message may travel directly to your mail ...


4

No, this is not necessary. Only if you send bulk mail, but then you're better off handing that to a service provider for sending it out, as they have far more experience in making sure that your e-mail reaches the target mailboxes. Also, just changing domain/subdomain does usually not work, as BAN's are largely based on IP addresses as well, or only on ...


3

There's nothing special you have to do to write your own From: header on an email. I do it all the time for my customer's websites I host on my servers, however, I make sure that my webservers' IP block is in their SPF records. As long as your customers add your.mail.servers.ipaddress(es) to their SPF records, you shouldn't get a forgery attempt because ...



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