ServerBuddies Support Blog

Checking your outgoing mail server (Is Port 25 blocked?)

Many email clients and services use port 25 for SMTP to send out emails. However an ISP (Internet Service Provider) may block port 25 in order to prevent spamming by its customers. Here is how you can check to see if port 25 is blocked on your network.

1. Type the following command:

2. View Results:
If port 25 is not blocked you will get a successful 220 response (text may vary).

If port 25 is blocked you will get a connection error or no response at all.

hotmail and yahoo mail spam flagging issue

If you have more than one domain on your server it is better to use our SPF Record to fix this issue.

For example:

Server is sending mail as mail.serverbuddies.com but when the receiving mail server performs a reverse PTR lookup, it finds serverbuddies.com MISMATCH The solution would then be to tell qmail that it is sending mail as domain.com instead of mail.serverbuddies.com.

Here is the fix.

Enable Alternate Port other than 25 or 587 (via SSH) in Plesk

Make a copy of /etc/xinetd.d/smtp_psa. For this walkthrough the new filename created is smtp_nonstandard. A command like this should work:

Add these lines to the copy you just made:

and change the service name to match the name of the file. A sample smtp_nonstandard looks like this:

# Restart xinetd:

# You should now be able to send mail through your server on port 2525. You may pick a different port if you use this method. We suggest choosing a high port number to avoid using commonly used ports on the internet.

Removing a mail server from the Spamhaus PBL

How to check if your IP is listed.

Spamhaus assists Internet service providers with preventing unsolicited email (spam) from passing through their mail servers. One of the tools Spamhaus employs is a “Policy Block List” (PBL) that lists addresses that get assigned to customers of dial-up, broadband, and hosting service providers. Those addresses are then blocked by default and have to be manually removed from the list when someone has a legitimate need to use one of those addresses to run a mail server (as many Slicehost customers do). It is therefore likely that a new slice, or one that hasn’t been used as a mail server before, will be on the Spamhaus PBL.

Being on the PBL doesn’t mean your address is blocked for spamming. The list is only there as a precaution against potential abuse. Spamhaus applies this policy to any IP addresses that could change hands from one customer to another. Their goal is to prevent computers that should not be sending email directly from being able to do so if they are compromised in some way.

Prevention of infinite mail loop with Auto Responder

This mostly happens when the mail account using autoreponder gets lot of spam mail, and as many of these spam mails use bogus From addresses, this account also recieves many mailer-daemon responses while replying to these bogus email addresses.

1) Edit /home/virtual/FILESYSTEMTEMPLATE/sendmail/etc/smrsh/responder.sh (This file is hardlinked into all the domains having autoresponder enabled as
/home/virtual/[domainname]/etc/smrsh/responder.sh)

and comment out:

so it looks like:

Then insert after it:

2) Create the file called auto.rc with the following lines:

Copy this file to /home/virtual/[domainname]/etc/ for all the domains using autoresponder.
(You may want to use virtDomain.sh to automatically copy or create this file when ever a new domain is added)

Now anything coming from MAILER-DAEMON or postmaster that goes to the responder will be sent to /dev/null.

Anything else will be sent to the responder.

Reference: http://parallels.com