There are mainly two ways to access emails for users. pop3 and imap protols are the commonly using protocol to access the emails.
POP3 (Post Office Protocol 3)
Port details:
POP3 Port: 110
SSL POP3 Port: 995
In POP3, all emails from your server is downloaded to the local machine. Please note that, you can not access it once you delete the email from email account with POP3. There are a lot of advantages and disadvantages are there with POP3.
Advantages of POP3:
>> Email is available when you are offline.
>> Email is not stored on the server, so your disk usage on the server is less.
>> All email clients (software) support POP3.
>> There is no advertising when you read your email.
>> Opening attachments is a quick and painless process because they are already on your PC.
>> There are often no size limits on the email you send or receive.
>> There is not a maximum size on your mailbox, except as determined by the size of your hard drive.
Disadvantages of POP3:
>> Can be much slower to check mail
>> Much harder to do server-side filtering
>> Mail is inaccessible from other machines
>> Opening attachments is a quick and painless process, unless the attachment has a virus payload in it.
>> All messages are stored on your hard drive eating up what is sometimes very valuable space.
>> Since all attachments are stored (downloaded) on your PC there is a potential danger of virus attack if they are not properly scanned by virus scanners. Then virus scans can only address 60% of attacks effectively leaving your PC to a great danger.
>> Email folders can become corrupted and sometimes lost forever. Recovering is often a painful exercise.
>> All messages are stored on your system, and privacy disappears when someone sits down at your machine. Even if your email reader is password protected, it is often possible for someone who knows what they are doing to read your email by using another application to open your mail folders.
>> It is unable to manage folders; it can manage only inbox folder
>> It cannot transfer selected portions of some messages
IMAP (Interactive Mail Access Protocol)
Port details:
IMAP Port: 143
SSL IMAP Port: 993
In this protocol emails are not stored in the local machine and there is an interactive connection to the server for accessing the emails.
Advantages of IMAP:
>> Email is available from any machine.
>> Email is stored on the server, so your email cannot be deleted/destroyed if your computer should happen to crash, be stolen, or destroyed
>> You can access IMAP mail via the web, without even needing a mail client installed. This means you can check your mail from someone else’s machine or even a public terminal and not have to worry about the security of your passwords.
If you read a message on one computer, it is read on any other computer you use to access your mail. If you reply to an email on one computer, that reply is available on any computer you use.
>> Robust folders for storing received and sent messages
>> Freedom for user to download attachments at will
>> Provision for determining message structure without downloading entire message.
>> Selective fetching of individual MIME body parts.
>> Server-based searching and selection to minimize data transfer.
>> Ability to append messages to a remote folder.
>> Ability to set standard and user-defined message status flags.
>> Support for simultaneous update and update discovery in shared folders.
>> New mail notification.
>> Ability to manipulate remote folders other than INBOX.
>> Remote folder management (list/create/delete/rename).
>> Support for folder hierarchies.
>> Suitable for accessing non-email data; e.g., NetNews, documents.
Disadvantages of IMAP:
>> Mail is not usually available if you are offline.
>> IMAP uses more bandwidth.
>> IMAP is slower