Simple Mail Transfer Protocol. A protocol for delivering e-mail from an end user to a server for storage and later retrieval by the intended recipient.

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12
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2answers
22k views

Test STARTTLS configuration of SMTP server

Is there an easy way to test an SMTP server to check for configuration issues associated with STARTTLS encryption, and report on whether it has been configured properly so that email will be encrypted ...
27
votes
4answers
17k views

What steps do Gmail, Yahoo! Mail, and Hotmail take to prevent eavesdropping on email?

I would like to ask what happens when an email is sent from gmail, yahoo or hotmail public web email services? I don't understand email protocols in details, but as far as I know email traffic is ...
-3
votes
0answers
20 views

SMTP mail flow, cannot be understand? [on hold]

SMTP mail server problem cannot be understand how it was gone. Can you help me to identify the attack or type of issue regarding this source and destination ? cloud shark - ...
-3
votes
1answer
40 views

How does SMTP facilitate sending spam? [closed]

My friend tells me that there are exist weakness of the Simple Mail Transfer Protocol (SMTP) that make make it easy to send spam. Is this true?
2
votes
2answers
87 views

TLS capable SMTP store-and-forward server — does it have to store private keys?

I know that email is inherently insecure anyway, but considering that pretty much everyone that I send email to is using a large, somewhat-trusted cloud provider, (hint, starts with G) I would expect ...
0
votes
1answer
112 views

Why doesn't outlook 2013 meet modern security standards?

It is required to turn on the allow less secure apps setting in order to be able to use a gmail account with outlook 2013, despite it is using the IMAP and SMTP services with SSL protocol enabled. ...
0
votes
1answer
39 views

OpenSSL gmail - receiving Please log in via your web browser and then try again

Using openssl as below when I do EHLO auth login and then enter my username and password I get the following error: Please log in via your web browser and then try again. Learn ...
0
votes
1answer
53 views

Mail server security: Mails to internal receivers with faked sender address

I noticed that I am able to send emails from my company's mail server to internal receivers from faked inhouse sender addresses without problem and I'm wondering if this should be supposed a security ...
3
votes
3answers
280 views

I'm getting spam e-mail…from myself?

I noticed yesterday that I had received spam e-mail, but my own e-mail address was listed as the sender. Naturally, I changed my password. This is probably a spoof, but I don't know enough about ...
0
votes
1answer
27 views

smtp-auth attack ?

it looks someone or something is trying to hack our Exchange. Exchange Server Transport Protocol Logs: it appears the internet facing IP on the firewall has not been locked down correctly, so is ...
2
votes
2answers
347 views

Rationale behind hiding originating IP address in emails?

Gmail has been hiding originating IP addresses for quite some time now. Hotmail and Yahoo have started doing this too. Apart from obvious privacy implications of revealing the sender's IP address, is ...
4
votes
2answers
70 views

Should I email contents of a https form submission

I am building an online registration form for a voluntary organisation in the UK and am considering data security measures. The form will be served up over https and there may be an optional payment ...
6
votes
2answers
884 views

How to prevent abuse of SMTP by sending spam emails?

I'm not an admin, I just created a website, and there's also a mail server on the server I payed for from my hosting provider. Most for what I learnt about mail servers is from an internet tutorials. ...
1
vote
2answers
2k views

How is mail automatically sent from my account?

Today I have received an email with an 'out of office' notification, as a reply to one of my emails, which I actually didn't send. I think it was sent automatically from my address, as a result of ...
0
votes
0answers
32 views

script for analysis of tcpdump log file

I'm trying to get the following metrics from my tcpdump log file: (1) one-way delay, (2) request/response delay, (3) packet loss, (4) overall transaction duration and (5) delay variation (jitter). ...
13
votes
4answers
14k views

How (in)secure is POP/IMAP/SMTP

I'm making a few assumptions about basic email security, and I want to confirm or clarify some of these points to make sure I understand the big picture. Please correct me where I'm mistaken: The ...
6
votes
2answers
845 views

Can (and should) TLS be strict about the ciphers it supports?

When trying to establish a TLS channel to outlook.com in order to relay SMTP traffic I get connection failures and have to continue without encryption. An example of such a connection: openssl ...
0
votes
3answers
64 views

Is VRFY command enabled on SMTP server usually considered a vulnerability? [closed]

Messing around I found a critical SMTP server with VRFY command enabled.
6
votes
1answer
646 views

How to reject e-mails spoofing your own domain targeting your employees at Office365?

One problem Office365 users deal with is that an external SMTP server can spoof the domain of an organization and send e-mails to the domain users; where the e-mails appear to be from employees of the ...
-1
votes
3answers
241 views

SMTP injection: where am I wrong?

On another thread a user was trying to use SMTP injections and, as a test, trying to inject a supplementary recipient for this email. My understanding of the issue preventing him from succeeding were ...
1
vote
0answers
70 views

How to inform other sysadmins their email encryption is broken [closed]

Does anyone have a good template email to use to send to remote system/mail/security administrators to alert them to the fact that emails to them would not be getting through either at all or securely ...
-3
votes
1answer
85 views

Recommendations for SMTP DoS [closed]

I have an opened SMTP server that allows me to send emails. The problem is that I can send a massive amount of emails (80,000+) to a specific mailbox and block all the other legitimate emails (that ...
0
votes
2answers
57 views

Is there a way to attack STARTTLS + certificate pinning probed from multiple places?

I just had this discussion on IRC and I have to admit I did not understand why other users were not convinced this would be enough... Let's say I would like to protect e-mails sent out from my ...
2
votes
4answers
229 views

How can I stop an IP from trying to use my mail server?

I have recently set up my first email server, and I look at the logs in /var/logs/mail.log to see what is happening, I notice this one IP does this multiple times every day for the last so many weeks ...
12
votes
1answer
2k views

How to study the packets sent by a keylogger

One of my friends runescape account got hacked through key-logger. He downloaded a runescape gold generator from a file sharing site and tried to use it. I have a strong doubt that it is a key-logger. ...
3
votes
1answer
189 views

is there a risk in increasing esmtp header line length against rfc5822 - asa/pix question

Have a question towards the 998 bytes limitation on the esmtp header line length. We have noticed the asa is dropping emails coming from various external mail servers with the header line length ...
4
votes
1answer
471 views

Phishing email from Avast - Headers look totally legit?

Below is the email with headers. I never registered on the site, so it's clearly phishing, but the links in the email point to the real Avast site. The delivery path also looks legit since both IP ...
3
votes
1answer
5k views

Perfectly secure Postfix MTA (SMTP) configuration

I want to secure my root server (further) service by service, starting with the SMTP service (Postfix MTA) as the most busy one. I the course of setting everything up, I read a lot about security and ...
3
votes
4answers
241 views

How webmail's authorisation should work?

I'm building a webmail client (like gmail). It allows the user to browse emails and send them. Under the hood, php uses IMAP and SMTP to talk with email server. user->webserver->mailserver When user ...
4
votes
1answer
2k views

SMTP injection, how it is done and what can it cause?

There are a few things that I dont understand about the injection. The injection is something along this line > . MAIL FROM: mail1@gmail.com RCPT TO: mail@gmail.com DATA EMAIL data . Here are ...
0
votes
1answer
635 views

Is my Postfix and Dovecot configuration secure?

Today I set up my first server with Dovecot and Postfix. These are excerpts from the configuration files: Dovecot: disable_plaintext_auth = yes ssl = required ssl_prefer_server_ciphers = yes ...
1
vote
1answer
191 views

Email account password change via email-to-script

I host a mail server (postfix and dovecot) and I wish to set up a password change feature (especially useful when creating a new address provided with a temporary password). Does my scenario has ...
3
votes
1answer
2k views

How can I find the process that is trying to use smtp to send email?

Previously I asked Who (which process) is calling curl? and I got very good answers (this answer in particular) which basically replace the curl binary with a shell script that logs each call to curl ...
0
votes
1answer
97 views

Receiving strange data over SMTP where body is one line of random characters

I have a website that has an smtp server open on port 25. There is no outbound functionality on the smtp server. We just parse attachments from our users, then 'queue' the email in a dummy queue. So ...
11
votes
3answers
1k views

Why enable SMTP STARTTLS if OpenSSL is dangerous?

There are a bunch of people in the anti-surveillance movement who are virtually demanding that I enable SMTP STARTTLS support in my environment, in order to enable opportunistic MTA-to-MTA encryption. ...
3
votes
1answer
1k views

What type of attacks will a SMTP server face if it does not have ratelimiting while sending mails?

Assume a web site with some kind of mailer option, that doesn't implement any rate limiting: This enables users to send an unlimited amount of email per second. Will SMTP face possible DoS attacks ...
173
votes
3answers
29k views

Don't understand how my mum's Gmail account was hacked

My mum (on Gmail, using Chrome) received an email from a friend's Hotmail address. She opened the email (very obviously a phishing email) and clicked a link in it. This opened a webpage with loads of ...
1
vote
2answers
83 views

What is the proper terminology for the various SMTP tunnel encryption solutions?

I'm writing up documentation and want to ensure that I'm using proper terminology. 1) What is the proper technical term for the SMTP tunnel encryption standard that typically starts on TCP/25, ...
-1
votes
2answers
396 views

What are the security risks for a business that has an insecure email system [closed]

For instance if the email system uses POP3 legacy protocol and SMTP but is not encrypted, yet the business continues to use it for daily purposes both internally and externally, what could be the ...
-9
votes
2answers
191 views
13
votes
2answers
1k views

What threats come from CRLF in email generation?

I have an application where a code scanner has identified CRLF injection possibilities in some classes related to email generation. I understand how CRLF injection could be used against me on ...
4
votes
3answers
1k views

How do you verify a certificate belongs to a domain?

I'm using PHP and trying to verify a SSL certificate belongs to the SMTP domain/IP I'm connecting to. Currently I can verify the certificate is valid using the following code $resource = fsockopen( ...
4
votes
3answers
1k views

Is STARTTLS a security-vulnerability?

After reading about STARTTLS and SSL and performing a scan/pentest at our server I have the next question regarding security: Is this STARTTLS warning below a security-vulnerability? And if so why? ...
1
vote
1answer
2k views

Email Spoofing by SMTP Message-ID?

Many of my users today got email from docs#@mydomain.com (where docs# was between docs0 and docs8 or so, and mydomain.com is obviously changed from my real domain name), with the sender name of ...
3
votes
2answers
597 views
1
vote
1answer
3k views

What are the realistic chances of email being intercepted via SMTP/TCP-IP? [closed]

Dear SMTP and TCP/IP network security gurus: I'm curious about what is the realistic risk of sensitive information (such as a email pdf attachment) being intercepted/read by a hostile party from a ...
2
votes
2answers
560 views

how to find out if a program sends data to internet (without permission)?

We have an application to save our customers data (some kind of CRM). This application has been written in Delphi and is a client/server application. This program apparently is sending out ...
0
votes
3answers
6k views

What is the hack attempt going on when I see: did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA

When I look at my sendmail logs, by far the most common "error" I see is the following: Nov 22 16:49:50 MyHostname sendmail[18832]: rAMMnj2u018832: [IP address redacted to hide the guilty] did not ...
1
vote
1answer
2k views

What are the ports used by Online Email Accounts such as Yahoo Mail, Gmail, etc.?

Let us say that I send an email using Yahoo Mail or GMail. Can this email be intercepted using a packet sniffer? On which port does the email travel? HTTP, SMTP, POP3?
1
vote
2answers
812 views

Issues with using a mail server that doesn't support authentication to send mail?

I have noticed the mail server we use at work (provided by our web-host) doesn't require any authentication to send mail through. I understand you easily spoof sender address' in emails, but I'm ...