Can we use ports other than 993 for IMAP in Microsoft hosted exchange servers?
Are these ports fixed from the Microsoft side OR any organization can configure its own port?
Please share the list of ports which can be used.
Can we use ports other than 993 for IMAP in Microsoft hosted exchange servers?
Are these ports fixed from the Microsoft side OR any organization can configure its own port?
Please share the list of ports which can be used.
First a bit of background:
TCP/UDP port numbers
In TCP (and UDP), the port number used by a server to receive connection is limited to the range 1-65535. (This wikipedia article lists all current ports numbers)
What port is used by an application usually depends on what protocol is used: common protocols have default port numbers assigned to them (known as "well known port"). These well-known ports are all in the range 1-1023 (and, in *nix OS, only root can bind to these port numbers).
The ranges between 1024 and 49151 is the "registered port range", used by applications for their own use: any organisation can register one of these port qas being used by ttheir application for a specific purpose.
Ports between 49152 and 65535 are in the dynamic port range and typically used to bind the client side of the socket connection.
Now, if an application exposes an IMAP4 protocol interface, it will use TCP port 143 by default and if is uses the secure version of the same protocol (IMAPS), it will use TCP port 993 by default.
These are, however, default values: the port number that a client will use to contact a server using the specific protocol by default. If you change that port number, then you will have to configure all your clients to use that new, non-default port and you must clearly indicate that change in the documentation.
In addition to that, you will also need to make sure no other application on the same IP address uses that same port: you can't have both HTTP and IMAP running on the same port on the same IP address. It's also strongly discouraged to use a well-known port for any other protocol than the one it is listed for.
Specific answers
Now, all the being said, here are the answers to your questions: