We’re rewarding the question askers & reputations are being recalculated! Read more.

Questions tagged [smtp]

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.

Filter by
Sorted by
Tagged with
1
vote
1answer
41 views

Does user need to keep updated with the certificates locally when using TLS with smtp?

https://wjianz.wordpress.com/2014/09/03/howto-installconfigure-msmtp-and-mutt-on-ubuntu/ I got GTS CA 1O1 as the common name instead of Google Internet Authority G2. What is the difference between ...
-1
votes
0answers
34 views

How figure out the google certificate url? [on hold]

I read this https://wjianz.wordpress.com/2014/09/03/howto-installconfigure-msmtp-and-mutt-on-ubuntu/ It says The issuer name is Google Internet Authority G2, we got the CA certificate here. ...
30
votes
5answers
68k 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 ...
0
votes
1answer
25 views

Spoofed email: can't determine Purported Responsible Address

I am studying the SMTP protocol and follow a course materials to setup a PoC spoofed email by talking with a SMTP server of our department. This is what I have right now: shuaiw@shuaicpu1:~$ telnet ...
1
vote
2answers
133 views

TLS 1.0 Deprecation and Mitigation Tactics

With the deprecation of TLS 1.0 on the horizon, I'm curious how others are handling connectivity and mail delivery issues for dated client environments. Lets face it, there are more environments live ...
1
vote
4answers
9k views

How a spoofing email site such as emkei works

I'm trying to understand how email spoofing works. After studying the technical process, I have finally understood that : 1)The spoofer will try to scan every ports of a smtp server to catch the mx ...
39
votes
2answers
11k views

How do email clients “send later” without storing a password?

Email clients like Spark for macOS have a feature where a user can send an email later, at any given time, even when the computer is turned off. An SMTP server needs a password based authentication, ...
1
vote
2answers
170 views

Weird character sequence in email subject

I've noticed that the subject in one of the spam emails looks like this in source: Subject: Offe=?UTF-8?Q?=EF=BB=BF?=r fr=?UTF-8?Q?=EF=BB=BF?=om C=?UTF-8?Q?=EF=BB=BF?=redi=?UTF-8?Q?=EF=BB=BF?=t On=?...
0
votes
0answers
69 views

Suspicious SMTP server client activity - non-ASCII queries

I've noticed some strange activities from some remote host connected to our SMTP mail server. Queries contains non-ASCII characters, below is the copy of one of them (to each query our server ...
0
votes
1answer
65 views

Block SMTP Connection That Doesn't Have Credentials

I am able to do the following and connect successfully without any type of credentials: telnet <IP Address> 25 When I am in I can verfiy emails, send emails, etc. I feel like this is a ...
0
votes
3answers
5k views

Can I spoof email?

I mean, if I would have my own SMTP (also, is it just about money or are there some limitations to running my own SMTP server?) and would just completely made up the mail (headers, spoofed IPs and ...
1
vote
1answer
74 views

Postfix SMTP - Can I use SSH public keys instead of sasl password

I am relatively new to managing mail server, although i am familiar with webhosting servers not running dedicated email services. Postfix is configured to use sasl-password authentication I have ...
1
vote
2answers
840 views

How to test if TLS is enforced for emails sent through SMTP? [closed]

We are planning to create a rule in Proofpoint to enforce TLS on all outgoing email. I need to test that the rule is working and emails are bouncing if the recipient SMTP server does not support TLS. ...
1
vote
2answers
1k views

Is it possible to fake the mail server address?

Suppose that I send an E-mail to someone. Is it possible to fake mail server address - for example, while I used my own local mail server, I send it as if it was sent from Microsoft mail server. (I ...
1
vote
2answers
213 views

How to extract intresting data from malicious e-mail header

Premise: I know pretty well how SMTP works, and how to read an e-mail header. I know what all the main fieds mean, but I couldn't know what to look for if I want to know if the mail is kind of ...
0
votes
2answers
80 views

What are recommendations for unblocking outbound SMTP traffic in an organization?

Our organization has blocked all outbound SMTP traffic under the assumption that we are preventing potential botnet spamming issues which lead to blacklisted IPs. However, I've seen other ...
1
vote
1answer
1k views

Is there a list of open mail relays I can use for a pentest? [closed]

I'm currently pentesing a client (with permission of course) and we are testing their email filtering capabilities. We want to check whether they reject mail coming from open mail relays, but I seem ...
50
votes
5answers
8k views

Why is end-to-end encryption still not default in mails?

I am not a cryptographer. Maybe that is why I don't see the issues with integrating PGP into SMTP. In my head: Lea requests the server of Luke's domain jedi.com to tell her the public key of luke@...
0
votes
0answers
80 views

Database in DMZ and SMTP relay

I have an application that talks with a database in the DMZ. There is a firewall between the apps and the db but our developer thought that they require a mail notification that is triggered from the ...
1
vote
2answers
182 views

Why would an attacker try SMTP login many times even though it is disabled?

I recently set up an SMTP server for myself to use, and I am getting some traffic from two IP addresses and none else (though for obvious reasons I will not state the addresses here). An example ...
1
vote
2answers
7k 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 "...
1
vote
2answers
1k views

It's still possible to email spoofing to Google

I would like to know if it's still possible to spoof an address from, for example, no-reply@company.com when sending to Gmail. I've tried sending a spoofed e-mail to other mail service and it performs ...
0
votes
1answer
76 views

Simple Mail Delivery Protocol (SMDP), where is it today? what do you think of it?

So I'm doing a research study on Simple Mail Delivery Protocol (SMDP) for those of you who don't know what it is, it's a new protocol for Email delivery that promises complete anti-spam filtering. ...
0
votes
2answers
65 views

Running open relay smtp in company network

We are producing IoT gateways which send out emails via SMTP protocol for user notifications. These IoT gateways are mainly used by corporate customers in intranets without access to or from the ...
2
votes
2answers
71 views

Domain offline - are unmaintained email clients a security risk?

I have just unregistered a domain. Now my mail client (Thunderbird) popped up a message saying that it cannot connect to the mail server. That's fine - for the moment. However, I wonder what would ...
1
vote
1answer
771 views

How to spoof a MIME-level email address

As a sysadmin, I need to send spoofed emails to ensure that the spoofing protection (DMARC, etc) is working. I think Emkei's Fake Mailer can be used to send emails spoofed at the SMTP / 5321.MailFrom ...
1
vote
2answers
171 views

How to detect SMTP proxy on public wifi?

For a small research project I want to collect characteristics of public wifi hotspots. One topic that came up was SMTP proxy - is there a way to detect a proxy or could I just check whether the ...
1
vote
1answer
455 views

SMTP Service STARTTLS Plaintext Command Injection

We are getting this vulnerability on SUSE Linux Enterprise Server 11. This vulnerability is getting triggered on port 587 for postfix. I have checked several links but I am unable to get any relevant ...
7
votes
2answers
619 views

Why are common services using implicit SSL not considered obsolete in the way that SMTPS is?

SMTPS (implicit SSL) has been deprecated/obsolete since SMTP+STARTTLS (explicit SSL) was defined in RFC2487. I'm not entirely clear on the reasoning behind that, but it was clearly considered a good ...
2
votes
0answers
344 views

Why is hotmail mail server providing an invalid certificate?

It seems that hotmail.com mail server sitting at hotmail-com.olc.protection.outlook.com is using a TLS certificate issued to mail.protection.outlook.com. Both the mail server hostname and TLS ...
0
votes
2answers
153 views

Can password be stolen when doing SSL/TLS-protected IMAP/SMTP in public network

My email password has been stolen most probably while I was on vacation in another country and was using hotel's (and maybe others, cannot remember) WiFi networks to read and optionally send emails ...
2
votes
2answers
1k 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 ...
15
votes
3answers
2k views

Can I expect my e-mail to be routed securely?

If I connect to my e-mail server via SSL (SMTP/SSL) and the recipient also only checks his e-mail via SSL (web/https or IMAP/SSL), does this - generally speaking - increase the security for the ...
3
votes
1answer
81 views

Why doesn't SMTP check that users are authenticated to send from an address?

I think it's a bit different from this question since it's about SMTP, but similar idea. Wikipedia says on email spoofing: MAIL FROM: - generally presented to the recipient as the Return-path: ...
1
vote
2answers
691 views

Close Port 587 - Ramifications?

Our recent PCI scan failed because "Plaintext authentication is allowed over unencrypted channel on SMTP." As such, our tech support suggested to close port 587. What are the effects of closing port ...
4
votes
2answers
462 views

How to securely store user-specific mail server credentials at the server side of a web application

I have an asp.net web app that generates emails when users perfrorm actions...these emails are generally notifications to other users that they should see/do something. The users can be internal to ...
4
votes
1answer
170 views

How secure is e-mail landscape right now?

In light of recent news about some flaws in PGP standard, I (a non-PGP user) started to think how secure are regular e-mails these days. I have found the STARTTLS Everywhere project, and they have a ...
2
votes
2answers
296 views

Can SPF be bypassed by using a shared email server?

As I understand it, SPF works by listing permitted SMTP server domains in the TXT DNS record of the domain you own. So if I own example.com and wish to permit a 3rd-party SMTP server at smtpexample....
0
votes
1answer
457 views

Is it possible to disable SSL over SMTP/POP to the mail server that enables SSL/TLS?

I'm using thunderbird where I can check the option whether I will use SSL/TLS or not. However in my company's server, SSL/TLS is enabled both on POP3 and SMTP. Is it possible to disable SSL/TLS on ...
0
votes
1answer
57 views

SMTU AUTH and compromised user

Recently I've set up two SMTP auth-enabled sendmails, and within a week and month both of them were used to send unsolicited mail using SMTP AUTH. Attackers were acting from different IP and using ...
1
vote
1answer
1k views

How to get the IP Adress of an email receiver

I am communicating through email with a scammer who is trying to by me mw own parcel of land. I already contacted the police but it could take 2 to 3 months before they start investigating. I want to ...
2
votes
2answers
5k 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 ...
3
votes
2answers
379 views

SSL/TLS compression attacks on mail servers (smtp)

Currently, we know few compression attacks on the SSL/TLS protocol (such as Crime or Breach). I wonder for few days if these attacks are practicable on a mail server (smtp). Is CRIME attack ...
7
votes
4answers
3k 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
513 views

Why did PHP 5.6 change how it handles SSL certificates?

I was using PHPMailer to send an email with SMTP. This time I used PHP 5.6. I received the following error. Warning: stream_socket_enable_crypto(): Peer certificate CN=`*.example1.com' did not match ...
4
votes
2answers
1k views

What happens if STARTTLS dropped in SMTP?

SMTP uses STARTTLS extension to upgrade SMTP to SMTP Secure (STMPS). According the the RFC, the client and server starts TLS as follows: S: <waits for connection on TCP port 25> C: <opens ...
6
votes
1answer
724 views

Why is still so easy to send phishing emails?

When I first started playing around with how SMTP worked over 20 years ago, I remember being somewhat surprised how easy it was to make an email appear in someone else's mailbox that looked like it ...
1
vote
2answers
840 views

Email Security Gateway vs Firewall [closed]

An email security gateway is an edge device such a router that serves for relaying the external network with the private network. It helps with detecting and blocking spams and phishing emails. That ...
0
votes
3answers
1k views

Is Open Port 25 on Web Server dangerous?

Port 25 of a web server is open. We dont have any email server, since we use google mail server, but still port 25 is open. Is it dangerous to keep it open? If it can be attacked then how it can be ...
64
votes
1answer
15k views

Why does Gmail (add accounts) using SMTP server recommend SSL instead of TLS?

I stumbled something interesting today when I was adding an account to my gmail one. Why is SSL boldly stated as recommended when TLS supersedes SSL? The links for SSL and TLS is the same: https://...