[Dovecot] change smtp port

[Giles Coochey]

On 2012-01-23 14:50, Charles Marcus wrote:
> On 2012-01-23 9:41 AM, Giles Coochey <giles at coochey.net> wrote:
>> On 2012-01-23 14:38, Amira Othman wrote:
>>> And there is no way to receive incoming emails not on port 25 ?
>
>> No.
>> http://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol
>
> Well, not precisely correct...
>
Now true, you can do anything you like internally, but if you want to 
listen and speak with the rest of the Internet, you should be RFC 
compliant.

RFC821
       Connection Establishment

          The SMTP transmission channel is a TCP connection established
          between the sender process port U and the receiver process 
port
          L.  This single full duplex connection is used as the
          transmission channel.  This protocol is assigned the service
          port 25 (31 octal), that is L=25.

RFC531
4.5.4.2.  Receiving Strategy

    The SMTP server SHOULD attempt to keep a pending listen on the SMTP
    port (specified by IANA as port 25) at all times.  This requires the
    support of multiple incoming TCP connections for SMTP.  Some limit
    MAY be imposed, but servers that cannot handle more than one SMTP
    transaction at a time are not in conformance with the intent of this
    specification.

    As discussed above, when the SMTP server receives mail from a
    particular host address, it could activate its own SMTP queuing
    mechanisms to retry any mail pending for that host address.