23 Jan
2012
23 Jan
'12
5:01 p.m.
On 2012-01-23 14:50, Charles Marcus wrote:
On 2012-01-23 9:41 AM, Giles Coochey giles@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.