Exim - Sender verify failed - rejected RCPT

Question

While checking on Exim's log messages I found many entries of the following message "Sender verify failed" "rejected RCPT" ... I 'm not an exim expert... I'm afraid Exim is not delivering 100% emails to recipients, because our Email Marketing Application its getting a lower OPEN RATE.

Can someone helpe understand this log messages? Is it my server saying "No Such User Here" or a remote server? 174.111.111.11 represents my server IP. Thanks

Exim log

2010-10-02 14:00:19 SMTP connection from myserverdomain.com.br () [174.111.111.11]:54514 I=[174.111.111.11]:25 closed by QUIT
2010-10-02 14:00:19 SMTP connection from [174.111.111.11]:54515 I=[174.111.111.11]:25 (TCP/IP connection count = 2)
2010-10-02 14:00:19 H=myserverdomain.com.br () [174.111.111.11]:54515 I=[174.111.111.11]:25 Warning: Sender rate 672.4 / 1h
2010-10-02 14:00:19 H=myserverdomain.com.br () [174.111.111.11]:54515 I=[174.111.111.11]:25 sender verify fail for <[email protected]>: No Such User Here
2010-10-02 14:00:19 H=myserverdomain.com.br () [174.111.111.11]:54515 I=[174.111.111.11]:25 F=<[email protected]> rejected RCPT <[email protected]>: Sender verify failed

2010-10-02 14:00:19 SMTP connection from myserverdomain.com.br () [174.111.111.11]:54515 I=[174.111.111.11]:25 closed by QUIT
2010-10-02 14:00:19 SMTP connection from [174.111.111.11]:54516 I=[174.111.111.11]:25 (TCP/IP connection count = 2)
2010-10-02 14:00:19 H=myserverdomain.com.br () [174.111.111.11]:54516 I=[174.111.111.11]:25 Warning: Sender rate 673.3 / 1h
2010-10-02 14:00:19 H=myserverdomain.com.br () [174.111.111.11]:54516 I=[174.111.111.11]:25 sender verify fail for <[email protected]>: No Such User Here
2010-10-02 14:00:19 H=myserverdomain.com.br () [174.111.111.11]:54516 I=[174.111.111.11]:25 F=<[email protected]> rejected RCPT <[email protected]>: Sender verify failed

2010-10-02 14:00:19 SMTP connection from myserverdomain.com.br () [174.111.111.11]:54516 I=[174.111.111.11]:25 closed by QUIT
2010-10-02 14:00:19 SMTP connection from [174.111.111.11]:54517 I=[174.111.111.11]:25 (TCP/IP connection count = 2)
2010-10-02 14:00:19 H=myserverdomain.com.br () [174.111.111.11]:54517 I=[174.111.111.11]:25 Warning: Sender rate 674.3 / 1h
2010-10-02 14:00:20 H=myserverdomain.com.br () [174.111.111.11]:54517 I=[174.111.111.11]:25 sender verify fail for <Luciene_souza_vasconcellos=[e-mail]>: No Such User Here
2010-10-02 14:00:20 H=myserverdomain.com.br () [174.111.111.11]:54517 I=[174.111.111.11]:25 F=<Luciene_souza_vasconcellos=[e-mail]> rejected RCPT <[email protected]>: Sender verify failed

Solution 1

The messages are Exim identifying two problems with the incoming email (server - sender):

• The server is trying too many times within a given amount of time (hammering)
• The "to" address and mailbox does not exist

Solution 2

Most probably your server tries to verify the sender's email address and it finds that there is no such address. It is a good, albeit not foolproof, method to filter out unsolicited email.

In order to verify this, the exim server connects to the remote SMTP server from which the mail originates accordig to the "MAIL FROM" command. If the server can't be reached, or if it doesn't know about that particular email address, the delivery is denied.

So, the error message is initially given by the MX server of "e-mydomain.com.br". Your server, when it doscovers that the email is originated from a nonexistent address, denies the delivery.

For this, the exim config contains entries like this:

deny message = Sender verify failed
     !verify = sender

Check your config and if you see something like this, then the cause of the errors is that your server denies mails from addresses which can't be verified.

In this case, you probably don't want to change it. Like I said, it is a good thing to check the sender. Real-world senders do have a valid email address, anyway.

Solution 3

To debug this, run exim -bh 1.2.3.4. This will open a simulated SMTP session as if someone connected from the IP address 1.2.3.4, except it also outputs a lot of debugging information (and it doesn't actually send any messages to anyone).

Start typing in SMTP commands - HELO test, MAIL FROM: [email protected] then RCPT TO: realuser@yourdomain.

Once the RCPT TO command has been entered, you should see the same failure message but this time there will be a lot more messages you can go through to work out where the rejection is happening.

Remember to include the HELO command above as omitting that can be one reason for rejecting the e-mail.

Comments

[Newtonx]

Thanks. I found out Default Email/Catch-all is disabled on Cpanel. Is that why my server is rejecting bounced messages delivered to email accounts generated by my Application in wich usernames does not exists like [email protected]? What is my server trying to do too many times?

[user48838]

Those were combined conditions messages/loggings, so the separate single event actions is not determinable through those.