Hot answers tagged

116

It is technically possible to send an email directly to the recipient's SMTP server from your computer. Looking at it from a historical basis, if the remote SMTP server is down, you want a system to automatically handle it and keep retrying it— hence you have an SMTP server. Similarly, in the old days, not all mail servers were connected all the ...


32

Why do I need an intermediate SMTP server to send mail? Why can’t my client (Outlook, Thunderbird) send messages directly to the recipient’s SMTP domain? In 1991—and most of the early 1990s and even earlier—you might be able to do what you describe. But the reality in 2015 is, while one can technically send an email to anyone from any machine that has a ...


19

No, it is not required to set up a DNS cache on the server. The server should use a caching DNS resolver that's somewhere nearby, but most hosting companies already run their own resolvers for the entire datacenter and configure servers to use them by default. By default, both Postfix and Dovecot use local accounts for everything. If you have a Linux account ...


15

Most residential ISPs block TCP port 25 (SMTP) in order to prevent you from participating in a spam network. If your PC becomes infected, your PC can start spewing spam at the behest of someone else.


12

Their functions are mainly the same, but the subtle differences are based on where they are located in the mailchain, hence they support sligtly different usages. SMTP Server is somewhat generic and can mean any server utilizing the SMTP protocol. However, in this context, it means the server to which a mail client (for example Thunderbird) connects to to ...


11

Have a listen to Security Now podcast #397. In the episode they talk about how ISP are blocking port 25 (among others including 135, 137, etc.) and are making it return as closed instead of stealth. Many big ISPs including Comcast, Cox and Verizon are blocking port 25 and there really isn't anything you can do about it, but there really isn't anything to ...


11

I was able to fix my problem by changing the postfix main.cf configuration to read: smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination instead of using smtpd_recipient_resrictions It turns out that after postfix 2.10.0, smtpd_relay_restrictions should be used instead of ...


11

It's possible. The two protocols are completely unrelated. IMAP doesn't care how you send mail, and SMTP doesn't care how you receive mail. In Thunderbird, the SMTP server settings work the same and should even be located in the same place. The real problem is that many domains use SPF to define a small whitelist of which SMTP servers are allowed to send ...


10

You can disable incoming SMTP by editing master.cf, just comment out the smtp and submission services. This will tell postfix not to spawn an smtpd process, which would listen on port 25 (587 for submission) for incoming SMTP connections.


10

I figured out a way to do this. Use the Gmail SMTP server. Create an application specific password. This is essentially the manual way to "send as an alias" with gmail. I don't know why they removed the Alias functionality, but this is how to make it work. I've written a more detailed step-by-step tutorial with screenshots and links here: http://...


9

Any business that wants to accept incoming email over the internet will need an SMTP server, so that facebook has one isn't unexpected. It is an incoming server, so won't accept facebook source addresses. It appears to be fairly standard, and wants standard headers: # telnet 66.220.155.11 25 Trying 66.220.155.11... Connected to 66.220.155.11. Escape ...


9

The first thing to make clear when asking "is ABC safe?" is to define your threat model. In this case, you have (and kudos for that): your threat model is your ISP being malicious and wanting to look at your (outgoing, presumably, since you ask about their SMTP server) e-mails. Against such a threat model, using the ISP's mail server does indeed present ...


8

If you are using the modern Outlook Web Application, in the top right corner you should see a settings button. Select the button and click Options from the drop down menu. On the resulting screen in the left column toward the bottom you should see an option to see POP/IMAP settings. Clicking on the link should bring up a pop up will all the information you ...


8

There is no way to monitor the sent mails in a clean way. You can only grep the details from the maillog of postfix. Here is an example: log='logfile of postfix' grep "status=sent" $log | \ egrep -ve 'postfix/(cleanup|pickup|master|qmgr|smtpd|local|pipe)' And also avoid the logs for dkim etc. If you need the count of mails then pipe on wc -l at the end.


7

This is behavior of Thunderbird is arguably poorly implemented, but you can add any account with any settings without contacting a server to verify those settings. TL;DR -- After initial account verification failure, manually enter your email server settings (including any bogus ones) and press "Advanced config" when it appears. Then press "OK&...


7

You can't Because of how email works, this is entirely impossible. Your mail client will deliver the message to your server, which will then pass the message on to another server, etc... until finally the message is passed to the destination server. Even then, the target user's mail client needs to recieve and view the message. Due to this chain, it is ...


7

Odd... I checked the email address with DNS Stuff's Mail Service Test Center tool and it showed the server was valid and accepted connections on port 25. I had no issue using the telnet command in your question, it appears the maximum email size is ~20MB: ~$ telnet mail.dgfip.finances.gouv.fr 25 Trying 145.242.11.31... Connected to mail.dgfip.finances....


6

Despite other assertions, ISPs can triviallly intercept any email you send through their servers - in fact they systematically do this all the time - for example by using spam filters (which are legit). They also almost certainly log metadata - including from address, to address, date at minimum. That said, SMTP is not a secure protocol and can be ...


6

The other answers are all excellent, and spam does have a lot to do with it. But there actually is a simpler, more generic, answer: features. Sending email through SMTP is actually a very complex undertaking. Even without spam, you wouldn't want to implement the whole feature set of the SMTP protocol in every email client; you are better off with a ...


5

There are still a number of outstanding bugs dealing with special characters on the AuthPass line in the /etc/ssmtp/ssmtp.conf file: https://bugs.debian.org/cgi-bin/pkgreport.cgi?repeatmerged=no&src=ssmtp#_0_3_4 These bug reports are specifically for the ssmtp page in Debian, but probably apply to others. Debian Bug report logs - #463196: ssmtp cannot ...


5

This can be achieved with transport_maps = hash:/etc/postfix/transport in main.cf #/etc/postfix/transport domain1.com local: user1@domain2.com smtp:smart.host1.com:25 domain2.com local: user1@domain3.com smtp:smart.host1.com:25 user2@domain3.com smtp:smart.host2.com:25 domain3.com local:


5

Configuration For SMTP port 465, ensure the Start TLS option is off in the $HOME/.msmtprc file: defaults auth on tls on tls_trust_file /etc/ssl/certs/ca-certificates.crt logfile /tmp/msmtp.log account ACCOUNT host mail.host.com port 465 from account@host.com user account@host.com ...


4

In Outlook Web Access: Go to Options in the top-right corner, Choose See all options. On the Account tab, Click the link Settings for POP, IMAP, and SMTP access. A window will pop up with the relevant settings, and information on whether the services have been disabled.


4

Good question, I really haven't seen any figures for this. I'm not sure, but I think many large companies now support SSL/TLS for inbound and outbound SMTP ("MX" mail delivery). This is normally optional and can be negotiated via StartTLS on port 25. Most SMTP servers do not require server to server TLS, however, as it would mean many would not be able to ...


4

Set smtpmail-smtp-user, smtpmail needs it to look up credentials in the authinfo file.


4

Go to cmd.exe then run cd c:\Inetpub\Adminscripts cscript adsutil.vbs set smtpscv/ vsi number /connectresponse “New banner here”


4

One possible reason is that the sender might simply be unable to reach the recipient's mail server directly. In the early days of email & SMTP, you had more than just Internet – you had Bitnet; UUCPnet/Usenet; Berknet; MILNET; DECnet; etc. all using incompatible protocols. A domain like sri-unix.uucp might not have had an IP address in DNS – only a MX ...


4

You are connecting to localhost via IPv6 (::1), but that address is not part of the "mynetworks" list. Change it to mynetworks = 127.0.0.0/8, <site IP>, [::1]/128 and it should work.


4

I think you can easily get it done through Powershell. Follow these Steps: Step 1 - Open CMD (Run as Administrator) Step 2 - Type Powershell (Hit Enter) Step 3 - Copy the below code in notepad first $EmailFrom = “Your email Address” $EmailTo = “Recipients email Address” $Subject = “The subject of your email” $Body = “This is just a test mail to verify ...


4

What you're missing is that nmap isn't the be-all-end-all checker of open ports. For one, it's a terrible idea to do a full-on port scan just to see if one single port is open. telnet works perfectly fine: shadur@huginn:~$ telnet gmail-smtp-in.l.google.com. 25 Trying 2a00:1450:4013:c01::1b... Connected to gmail-smtp-in.l.google.com. Escape character is '^...


Only top voted, non community-wiki answers of a minimum length are eligible