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I run a little greeting cards web-site on VPS. It uses Postfix to send greeting cards to clients. Currently the volume is tiny, about 10-20 cards per day. There is absolutely no spam activity (at least to my knowledge) and my IP is not blacklisted in such organizations as MAPS, www.abuse.net, etc.

I noticed that there are cases when the emails are not delivered. There are 3 major types of faults:

1. User mailbox rejections

Messages:

  • 550 Message was not accepted -- invalid mailbox
  • Recipient address rejected: User unknown in relay recipient table (in reply to RCPT TO command)
  • The e-mail address you entered couldn't be found. Please check the recipient's e-mail address and try to resend the message. If the problem continues, please contact your helpdesk.
  • 550-5.1.1 The email account that you tried to reach does not exist. Please try 550-5.1.1 double-checking the recipient's email address for typos or 550-5.1.1 unnecessary spaces. Learn more at 550 5.1.1 http://support.google.com/mail/bin/answer.py?answer=6596 bk8si48484441wjb.30 (in reply to RCPT TO command)
  • etc

I get this for different mail servers including gmail, yahoo, mail.ru, etc. I admit that some users may make a typo but it appears that the rate is way too high, I cannot believe there so many typos can be made.

2. Greylisting

One server reports this:

host mxs.ukr.net[195.214.192.100] said: 451 http://ukr.net/mta/std3.html?my_ip (in reply to RCPT TO command)

The link goes to the page on that server where they suggest "to properly setup queue runners".

3. Unauthorised requests

host mx9.i.ua[82.144.223.46] said: 451 Unauthorised request. Try again later (in reply to RCPT TO command)

Here are my questions, applicable to my case:

  1. How difficult would be to fix these issues?
  2. Would you recommend to hire a professional IT-specialist to configure email server?

Any help is much appreciated.

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    if the rate of mistyped adresses to freemailers is unusually high I'd check your logs if spambots are trying to abuse your form. make sure you have captchas or similar anti-bot measures in place.
    – Gryphius
    Jan 4, 2013 at 17:32
  • The thing is that I have 10 cards per day on average so I am not sure if spambot would do such tiny sending. Do you think it is possible?
    – Alex
    Jan 4, 2013 at 17:37
  • Unless you have real users complaining that their cards are not being delivered, the generic answer to questions like this is, "Welcome to the Internet". Jan 5, 2013 at 0:44

2 Answers 2

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You can't really "fix" a user who mistypes an email address. So there's not much you can do about those bounces.

As for the two greylisting examples you gave, just wait them out; postfix will resend the messages.

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  • Could the "mailbox not found" type messages be related to my side?
    – Alex
    Jan 4, 2013 at 17:31
  • Only if you screwed up the email address, and not the user. Jan 4, 2013 at 17:32
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    Right. Postfix will resend the message automatically, if it's running. Its queue runner is named qmgr and should be one of the processes running on your server. Jan 4, 2013 at 17:36
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    The "Unauthorised request" is just another greylisting. Jan 4, 2013 at 17:37
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    Yes, essentially, what you experience is normal and there isn't much you can or need to do about it.
    – daff
    Jan 4, 2013 at 18:21
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1. There may be mistyped addresses or your software writes them incorrect but it is unlikely a server problem.

2. and 3. Errors starting with 4** is not permanent and mail server should store such emails in queue and deliver later. This feature is exploited by graylisting, because most spammers send e-mails using scripts and do not implement queue. So it is a normal behavior, that mostly do not require fixing. First check, if those emails do not get delivered later.

More on 3. Error number is a real error reason. Text after it can sometimes be misleading. Better check, what specification says about error number.

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  • Could you please tell me how to check if those emails had been eventually delivered?
    – Alex
    Jan 4, 2013 at 18:10
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    Check your mail queue with the mailq command to see which messages are still held and review the Postfix log files (probably /var/log/mail.log) once the queue is empty. The logs will tell you if the messages were delivered properly or, if not, what happened to them.
    – daff
    Jan 4, 2013 at 18:18

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