Server Fault Stack Exchange
Server Fault Stack Exchange

Questions tagged [smtp]

SMTP is the Simple Mail Transfer Protocol, the most recent standard of which is defined in RFC 5321. It's the Internet standard for sending and receiving email.

Some characteristics of SMTP (Simple Mail Transfer Protocol):

  • The default port is TCP port 25 and new submissions (MSA) is port 587.
  • Although depreciated, some services still use port 465 (SMTPS) to support legacy applications.
  • It is used to transmit outbound mail, and mail servers (which listens on port 25) receives mail on port 25.
  • It should not be confused with POP3 / IMAP which is an actual store for the e-mail. SMTP messages are received by the receiving server and then an MTA moves it to the POP3 / IMAP mailbox where it is normally retrieved using a POP3 / IMAP client.

See Also:

RFC5321

3133 questions
8
votes
2 answers

Is setting up my own SMTP server to send email a waste of time with regards to deliverability?

I have a dedicated host serving a few domains I manage. I host my own email and IMAP server. The server is at buildoneforme.com with IP address 144.76.81.247. I think reverse DNS is working: $ host 144.76.81.247 247.81.76.144.in-addr.arpa domain…
user7406
  • 233
  • 1
  • 2
  • 5
8
votes
5 answers

Reject incoming emails that use your own domain as sender

It would be nice to reject incoming emails which use one of my virtual domains as sender address while not being a legitimate user of mine. I know that I can reject incoming emails which use an existing alias/account name using…
Zulakis
  • 4,153
  • 14
  • 48
  • 76
8
votes
2 answers

How to set the username and password for smtpd in Postfix?

I've set up Postfix as SMTP server by adding this configuration to main.cf: myhostname = foo.com mydomain = foo.com myorigin = $mydomain smtpd_sasl_path = private/auth smtpd_sasl_auth_enable = yes broken_sasl_auth_clients =…
Overv
  • 182
  • 1
  • 1
  • 8
8
votes
1 answer

450 4.7.1 Client host rejected: cannot find your hostname

I have a Postfix/Dovecot email server which fails to deliver emails to some addresses. Here's an example of what is says: : host mail.da.net.ua[91.213.154.4] said: 450 4.7.1 Client host rejected: cannot find your hostname,…
src091
  • 277
  • 3
  • 4
  • 8
8
votes
3 answers

Will mailing lists "break" if SPF is too restrictive?

I have recently configured my own mail server (Linux-based postfix + dovecot scenario). This is just for personal use - I have no bulk mail going out, no automatically generated mail outbound from the host, nothing like that. I've gone through the…
Chris Tonkinson
  • 475
  • 2
  • 6
  • 19
8
votes
3 answers

Postfix - accept all email to any user at any domain

I need to configure an SMTP server to accept any email to any address that might happen to reach it on port 25 and deliver it to a local mailbox (i.e. a spam sinkhole) The default supported MTA on my O/S is Postfix, of which I have no experience. I…
Alnitak
  • 21,191
  • 3
  • 52
  • 82
8
votes
4 answers

POSTFIX main.cf permission denied

I am trying to set up a postfix server for smtp relay. Centos 5.5 I have followed http://mhawthorne.net/posts/postfix-configuring-gmail-as-relay.html but am getting a FAILED error when trying to restart or reload postfix. When I do: cat maillog I…
MG55114
  • 83
  • 1
  • 1
  • 4
8
votes
1 answer

Cisco FWSM -> ASA upgrade broke our mail server

We send mail with unicode asian characters to our mail server on the other side of our WAN... immediately after upgrading from a FWSM running 2.3(2) to an ASA5550 running 8.2(5), we saw failures on mail jobs that contained unicode and other text…
Mike Pennington
  • 8,305
  • 9
  • 44
  • 87
8
votes
2 answers

Dealing with SMTP invalid command attack

One of our semi-busy mail servers (sendmail) has had a lot of inbound connections over the past few days from hosts that are issuing garbage commands. In the past two days: incoming smtp connections with invalid commands from 39,000 unique…
mark
  • 81
  • 3
8
votes
1 answer

Mail queue retry interval practices

I'm configuring a custom made mail queue. The thing is there can be errors sending mail. Normally, one won't know the reason why the mail didn't reach it's destination. So the most simplistic solution is to try to send the mail again. Here are some…
András Gyömrey
  • 204
  • 1
  • 3
  • 7
8
votes
5 answers

How can email be resent that has been delivered to the Badmail folder in IIS?

We have IIS setup as an SMTP relay. A relay security error caused the outbound emails to be dropped to the badmail folder for the IIS SMTP Service. Is there any standard method for attempting to retry delivery of these emails?
catalpa
  • 321
  • 1
  • 2
  • 9
8
votes
2 answers

How to add DKIM feature to the IIS 7.5 - Windows Server 2008 - DomainKeys Identified Mail

How to add DKIM feature to the IIS 7.5 - Windows Server 2008 DomainKeys Identified Mail
Furkan Gözükara
  • 556
  • 2
  • 10
  • 27
8
votes
1 answer

how can i disable outbound mail in postfix?

i want to be able to send mail to someuser@localhost but not allow any mail to go out to the outside world from anyone to anyone. i've seen multiple entries about how to filter or restrict outgoing mail, but it seems like there should be a simpler…
tatere
  • 83
  • 1
  • 1
  • 3
8
votes
2 answers

Can I have an MX record for a 3rd level domain?

I have mail working for continuumconcepts.com right now. My mx records point to my assigned google postini servers. Works great. I have another server out in the wild that is completely disconnected from this network, and I have named it…
Christopher
  • 1,381
  • 1
  • 12
  • 22
8
votes
2 answers

Custom headers in Email lost?

I have some questions about custom mail headers Does anybody know of any mailserver which deletes proprietary/custom headers when being transmitted to its destination? Is there a header you can set in order to force a mail client to return a certain…
Atmocreations
  • 179
  • 3
  • 10
1 2 3
…
99 100