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Email delivery?

Email delivery?

Someone is

mail delivery email delivery? - maildelivery - Email delivery?

A mailbox full of mail against a blue and puffy white cloud sky

telling me just type the recipient email address to send an email. Sound familiar to you? He or she is not wrong. To send an email you first must know his or her email address but did anyone tell you how an email is delivered and why he or she did not receive my email.

Let me explain how an email is delivered. Most people are sending an email knowing only recipient email address. But sending email are more than just are knowing the other party email address. The most crucial thing for sending email is actually the DNS. without DNS, the mail server is handicapped and does not know where and how to deliver your email. DNS consists of records, it is like a directory to tell you where you are hosting the mail server and where to find you. With the DNS, your email is delivered to the destinate mail server and mailbox eventually.

Sometimes your recipient will claim email was not delivered to him or her. How did this happen? There are a few common reasons why an email was not delivered.

  1. Mistyped email address, this common mistake that people made, an email address is mistyped and sent wrongly and was not sent.
  2. Email has gone to junk box and not knowing the email did arrive but was never in the inbox.
  3. Some mail server allows users to filter their emails because of spam emails. Sometimes keyword related filtering could have wrongly filtered your email.
  4. Your mail server IP is blacklisted by the popular DNSBL. It was not you but someone account is compromised and sending spam emails. This can cause your mail server IP to be blacklisted. At such situation, your email will be treated as spam email and bounced or filtered.
  5. Email is showing delivered as sent. This can be due to a bug in the mail client and it is not delivered to the mail server. This can happen to an outdated application.
  6. It is rare but it happened the email is caught in the sender or recipient mail server mail queue due to many reasons. When the email is caught in the queue it will not deliver to the user mailbox.

OpenVZ vs KVM

OpenVZ is an OS-level virtualization technology. This means the host OS is partitioned into compartments/containers with resources assigned to each instance nested within.

In OpenVZ there are two types of resources, dedicated and burst. A dedicated resource is one where the VPS is guaranteed to get such if requested; these are “yours”. Burst resources come from the remaining unused capacity of the system. The system may allow one VPS to borrow resources like RAM from another VPS when the second one is not using them. Since it is borrowing, such resources have to be returned as soon as possible. Should the other VPS want their dedicated resources back, your processes might become unstable or terminated.

Since OpenVZ is an OS level virtualization, It consumes far less resources per VPS container than a full virtual environment. On two hosts with identical hardware and subscription rates, OpenVZ should perform better than KVM because it doesn’t do full emulation. For example, it doesn’t need to run multiple full OS kernels, as it can share the single kernel between multiple VPSes. The result is significant memory and CPU savings. In fact, most of the kernel memory usage is not charged to the VPS at all, instead it is only charged what each particular VPS needs in addition to the main kernel.

KVM is a hardware virtualization technology. This means the main OS on the server simulates hardware for another OS to run on top of it. It also acts as a hypervisor, managing and fairly distributing the shared resources like disk and network IO and CPU time.

KVM does not have burst resources; they are all dedicated or shared. This means resources like RAM and diskspace are usually much harder to overcommit without endangering all user data. The downside with KVM is that if the limits are hit, the VPS must either swap, incurring a major performance penalty, or start killing its processes. Unlike OpenVZ, KVM VPSes cannot get a temporary reprieve by borrowing from it’s peers as their dedicated resources are completely isolated.

Because KVM simulates hardware, you can run whatever kernel you like on it (within limits). This means KVM is not limited to the Linux kernel that is installed in the root node. KVM can also run other x86 operating systems like BSD and Microsoft Windows. Having a fully independent kernel means the VPS can make kernel modifications or load its own modules. This may be important because there are some more obscure features that OpenVZ does not support.

Why some go for shared web hosting?

Some might ask, why are they going for shared web hosting? While VPS at vastspace is so cheap and you get dedicated IP and services. Unlike the shared web hosting, everything is shared and you are paying extra for a dedicated IP. There are many reason why shared web hosting is better than VPS.

  • You don’t need a dedicated IP.
  • Less budget.
  • Cannot estimate the incoming traffic.
  • Managed and updated by web hosting provider.
  • Do not need the knowledge to operate a VPS.
  • You are not sending emails, shared IP may get black listed easily.
  • You want to use shared resources, so you can stretch when you need more for less populated and powerful server. May not the case while many web hosting provider can limit your resources especially in Linux.

Virtual Private Server, do you need one?

A Virtual Private Server (VPS) can be a virtual machine offered just like a service by a web-based hosting service.

A Virtual Private Server runs a unique copy from the operating-system, and customers have superuser-level utilisation of that operating-system instance, to enable them to install almost any software that runs using that OS. For several purposes they are functionally comparable to a separate physical server, and being software-defined, could be a much more easily created and configured. They are priced reduced than the usual similar physical server, speculate they share the particular physical hardware as well as other VPSs, performance may be lower, and may depend around the workload of other instances on one hardware node.

 

The pressure driving server virtualization is comparable to what brought to the introduction of time-discussing and multiprogramming previously. Even though the sources continue to be shared, as underneath the time-discussing model, virtualization supplies a greater degree of security, determined by the kind of virtualization used, because the individual virtual servers are mainly isolated from one another and could run their very own full-fledged operating-system which may be individually rebooted like a virtual instance.

Partitioning just one server to look as multiple servers continues to be more and more common on microcomputers because the launch of VMware ESX Server in 2001. The physical server typically runs a hypervisor that is given the job of creating, releasing, and handling the sources of “guest” os’s, or virtual machines. These guest os’s are allotted a share of sources from the physical server, typically inside a way the guest is unaware of every other physical sources save for individuals allotted into it through the hypervisor. Like a Victual Pirvate Server runs its very own copy of their operating-system, customers have superuser-level use of that operating-system instance, and may install just about any software that works on the OS however, because of the quantity of virtualization clients typically running on one machine, a VPS generally has limited processor time, RAM, and disk space.

Although VMware and Hyper-V dominate in-house corporate virtualization, due to their cost and limitations they’re less frequent for VPS providers, which rather typically use products for example OpenVZ, Virtuozzo, Xen or KVM.

A lot of companies offer vps hosting or virtual dedicated server web hosting being an extension for website hosting services. There are many challenges to think about when licensing proprietary software in multi-tenant virtual environments.

With unmanaged or self-managed hosting, the client remains to manage their own server instance.

Unmetered hosting is usually offered without any limit on the quantity of data-transferred on the fixed bandwidth line. Usually, unmetered hosting is provided with 10 Mbit/s, 100 Mbit/s or 1000 Mbit/s (with a few up to 10Gbit/s). Which means that the client is theoretically able to utilize ~3 TB on 10 Mbit/s or as much as ~300 TB on the 1000 Mbit/s line monthly, although used the is going to be considerably less. Inside a vps, this is shared bandwidth along with a fair usage policy ought to be involved. Limitless hosting can also be generally marketed but generally restricted to acceptable usage policies and tos. Offers of limitless disk space and bandwidth will always be false because of cost, carrier capacities and technological limitations.

How to schedule a backup Job on Cloud Server

How to schedule a backup Job on Cloud Server

backup_panel How to schedule a backup Job on Cloud Server - backup panel - How to schedule a backup Job on Cloud Server backup_job How to schedule a backup Job on Cloud Server - backup job - How to schedule a backup Job on Cloud Server backup_email_notification How to schedule a backup Job on Cloud Server - backup email notification - How to schedule a backup Job on Cloud Server kaspersky_endpoint How to schedule a backup Job on Cloud Server - kaspersky endpoint - How to schedule a backup Job on Cloud ServerEach Cloud Server comes with 2 free backup instances at no cost regardless of backup size. Additional backup instances can be ordered at only $10 /monthly. This is an useful feature to customers make changes to their files often and requires a roll back in case of any mishaps.

To perform a manual backup and schedule backups are very easy tasks with our control panel, just few clicks away and the hassle-free backup feature will send you an email notification if whether the backup is successful or unsuccessful that requires attention and rectification.

Control panel of the cloud server How to schedule a backup Job on Cloud Server - backup panel - How to schedule a backup Job on Cloud Server

 

Scheduling Backup Job for cloud server How to schedule a backup Job on Cloud Server - backup job - How to schedule a backup Job on Cloud Serverdaily backup report for cloud server How to schedule a backup Job on Cloud Server - backup email notification - How to schedule a backup Job on Cloud Server

 

 

 

Outlook 2013 IMAP Sync Troubles

Recently, I’m experiencing issue with IMAP Sync troubles with my Outlook2013. Many articles point to  the direction on the update KB2837618 and KB2837643 were released by Microsoft on 12 Nov 2013 that might have caused the hiccups. However, I don’t recommend un-installing these updates as they add some IMAP improvements and you’ll have a better IMAP experience with these updates.

I personally recommend these methods;
The first, and I reckon this is the most effective method is to add Inbox to the IMAP root.
To do this, go to File, Account Settings and double click on your affected IMAP account. Click “More Settings” button then switch to the “Advanced” tab.
In the Root folder path field type Inbox. Exit the dialog and perform a send and receive.

However, there are 2 things you need to take note of;
a. If the Inbox is not your root folder, setting Inbox as the root won’t work, as it will hide all of the other folders.
b. The rules and alerts with folders specified will be disabled due to errors that these locations are no longer exist.

If that doesn’t work, try disabling the option to show only subscribed IMAP folders.
Right click on the IMAP Inbox folder and choose IMAP folders. At the bottom of the dialog is an checkbox for When displaying hierarchy in Outlook, show only the subscribed folders. Remove the check then close the dialog to return to Outlook. Click Send and Receive.

How To Set Up Master Slave Replication in MySQL

It’s pretty straight forward to setup Master and Slave replication that might sound complicated. It’s obvious that you 1st need two MySQL running instances and identify which is your master and which is your slave.

On your Master MySQL configuration file, vi /etc.my.cnf
 server-id = 1
 log-bin = mysql-bin
 log-bin-index = mysql-bin.index
 expire-logs-days = 10
 max-binlog-size = 100M
 binlog-do-db = newdatabase

Restart MySQL:service mysqld restart

A new SQL user needs to be created on the master:

create user mysqslave;
 create user 'mysqlslave'@'*';
 grant replication slave on *.* to mysqlslave identified by 'NEWPASSOWRD';
 flush privileges;

Next we need to extract some information on the Master MySQL with this command
show master status G

You will probably see something similar
*************************** 1. row ***************************
File: mysql-bin.000001
Position: 199
Binlog_Do_DB: newdatabase
Binlog_Ignore_DB:
1 row in set (0.00 sec)

Go to Slave MySQL server
Open up my.cnf and insert these

server-id=2
 master-connect-retry=60
 relay-log=slave-relay-bin
 relay-log-index=slave-relay-bin.index
 replicate-do-db=newdatabase

save and service mysqld restart

Now enter MySQL admin with root to insert this

change master to
 master_host='DNS_MASTER_IP',
 master_user='mysqlslave',
 master_password='NEWPASSOWRD',
 master_log_file='mysql-bin.000001',
 master_log_pos=199;
 start slave;

Now, check status with
 show slave status G

Look for error if any. Common mistake is usually on the master_log_pos is wrong if you have cut and pasted my command from this tutorial 😛

Congratulation, you have completed the Master and Slave MySQL replication.

“Screen” is very useful working with multiple shell windows on a Single SSH Session

The 1st thing I would tell a junior engineer, learn how to use “screen”. It’s extremely important tool allowing us to run scripts or commands in their own virtual window within the terminal, essentially allowing us to have a terminal on multi-tasking environment where we can switch between windows or another users at will. These are useful features that may help you in your daily administration tasks.

  • Use multiple shell windows from a single SSH session.
  • Keep a shell active even through network disruptions.
  • Disconnect and re-connect to a shell sessions from multiple locations.
  • Run a long running process without maintaining an active shell session.

 

If you do not have screen, then you can install it easily from an RPM or the package file for your system. For example, on CentOS you can install screen with yum: yum install screen

Basic but useful command with Screen
List a particular users screen sessions:

screen -list username/

(it’s important to have forward slash)

List your own active screen sessions:

 screen -ls

Re-attach to  users screen and session:

screen -x username/shared-session

Start a screen session and give it a unique name:

screen -S desired name

Detach from a running screen session leaving it running in the background:
Hit the key combination: Control + A/a + D/d (not case sensitive)
Re-attach to a specific screen you’ve named:

 screen -R "the screen name to be re-attached"

Power detach a screen that you are logged into from another location:
This is helpful if you’ve been accidentally disconnected from ssh while in a remote screen session and it’s still attached.

screen -D "the screen name to be detached"

Website is not showing up on a newly setup VPS with cPanel

In spite of the DNS and Zone records have been filled in correctly, website is still showing the cPanel Default Page. This is usually caused by IP has been wrongly assigned on WHM during setup of the account.

  • If you 2 or more IP address on your VPS, check the domain name has been assigned to the correct one that has been used in your DNS Zone records.
  • If you have only been assigned with only 1 IP address, verify the IP address beside your domain name in WHM under List Accounts from the side menu. If the IP address is different with your assigned IP, this is likely you have a mis-configured cPanel or the shared IP has not been configured correctly. To correct this, find Basic WHM/ cPanel setup, scroll down to shared IP section [* The IP address (only one address) that will be used for setting up shared IP virtual hosts.], update the IP with the correctly assigned one and save changes. Next, select Change Site’s IP address from side menu and update the IP for the domain accordingly.