Email Issues

1) Put the client’s domain name in -- http://centralops.net/co/DomainDossier.aspx and check the DNS and MX record of the client. Make sure that the domain is resolving from our servers. Generally the MX record is set as domain name if it is something else; tell the client that the MX record is not pointing to our servers. You can also check the MX records at – http://dnsstuff.com
2) Login into his cpanel and create a test email account and try sending and receiving emails to the test yahoo account (supp0rt_test@yahoo.com). If you are able to send and receive emails then let the client know about it and ask him whether he is not able to send/receive emails from a particular account.
3) The domain’s entry should be there in /etc/userdomains and /etc/localdomains if the client is using our mail servers. If the client is not using our mail servers entry for his domain should not be there in the /etc/localdomains. It should be in /etc/remotedomains.
4) Sometimes forwarders don’t work when customer sets domain forwarding from his control panel as well as email forwaders. This is called dual forwarding which does not work.
5) The permissions of the mail folder should be 770 and the ownership should be username.mail. The permissions of the inbox file should be set to 660.
6) Check the quota of the email account and the main account. Also the quota of the email account should not be set to ‘unlimited’.
7) Main Email Account – When an account is created on the server by default an email address is created with his username which is the main email account. This email account is accessed by directly using the username name instead of username@domainname. Also check there is no email account created in the name of main account. For eg eds.co.in is a domain having username eds there should not be any other email account having the same email address i.e. eds@eds.co.in. Clients cannot change or delete this main email account. They can change there main account only by changing the cpanel username.
8) If a client has given that he is not able to send and receive email at a particular email address the do the following –
• abcd@abcd.com – client’s email account
• xyz@xyz.com – email account where client is not able to send/receive email.
a. Check from which server the domain xyz.com is resolving. If it is not resolving from our servers entry for it should not be there in /etc/localdomains.
b. Try to send email from the SSH using – mail –vv xyz@xyz.com. Check the error message that you get while sending the email. If you are not able to send emails from the root then give the commands – host xyz.com and dig xyz.com. If you are getting ‘network unreachable’ then make sure that the ip of xyz.com is not blocked on our servers. Also try to traceroute the domain and check that the network is not interrupted or unreachable.
9) Sometimes there is problem with ISP's of customers as they block port 25 for SMTP connections. In this case ask customers to use the port 26 for SMTP. Port 110 is used for pop and there is no alternate port for it. Port 465 is used for secure SMTP and port 995 is used secure pop..
10) Sometimes I've seen IP's of customers getting blocked in /etc/exim_deny list which disallows customers from particular IP's to communicate with mail server. IP's get blocked for many reasons, mostly for mail bombing and mass mailing. In this case ask the ip of his local machine i.e. the one he gets at http://whatismyip.com and and delete it from /etc/exim_deny.
11) Many times email transfer is interrupted by ISP's servers and they don’t allow the message to get transferred successfully. Try to figure out this from /var/log/exim_mainlog as the logs show such error very clearly. To understand the exim_mainlog logs please see the following example –
“2005-05-13 01:40:19 H=(70.84.100.194) [220.79.119.149]:3286 I=[70.84.100.194]:25 F=<Spence4Figueroa@math.uu.nl> rejected RCPT <maddox@audiokingpin.com>: Dictionary attack (after 4 failures): No Such User Here ”
• 2005-05-13 01:40:19 -- Time when mail was sent/received.
• H= (70.84.100.194) [220.79.119.149]:3286 -- This is an inbound smtp connection its claiming to be the mailserver ‘70.84.100.194’ (H= (70.84.100.194)) its IP address is 220.79.119.14 and 3286 is the port it connected from.
• I= [70.84.100.194]:25 -- It is our server's IP and port.
• F=<Spence4Figueroa@math.uu.nl> -- Who the email is from.
• Rejected RCPT -- This is the error.
• maddox@audiokingpin.com -- Email address where the email is sent.
• Dictionary attack (after 4 failures): No Such User Here -- The reason why the email was rejected. IP of sender gets blocked in /etc/exim_deny file which is defined in /etc/exim.conf as disallowed IP's for email communication.