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Questions tagged [starttls]

STARTTLS is the SMTP command to connect to email servers securely over TLS (formerly SSL). Use with an email server tag like [postfix], [exchange], etc.

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Postfix client submission using TLS

I recently set up a Postfix mail server on Ubuntu to relay emails from my apps to Office365. Postfix to O365 works without problem but I also want my apps to connect to Postfix using TLS where ...
smwk's user avatar
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Postfix: Mail servers of certain providers are unable to send mail to my Postfix server / insufficient security / SSL alert number 71

There is big German email hoster (web.de) whose mail servers are not able to send mails to my self-hosted Postfix server. I found similar reports, but the published solutions always were misconfigured ...
user2690527's user avatar
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2 answers
332 views

How do I properly issue Let's Encrypt certificate for my mail server?

How do I properly issue Let's Encrypt certificate for my Postfix mail server? Right now I have a self-signed certificate and I get these messages it cannot be trusted. I did certbot --nginx certonly -...
m27's user avatar
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postfix wrappermode depending on destination

My ISP accepts mail on port 465 thus requiring smtp_tls_wrappermode = yes. However, I also have another internal server, to which I forward mail on port 25 using STARTTLS, but with ...
Lars Hanke's user avatar
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Specific incoming mail to postfix rejected by sslv3 alert bad certifica te:s3_pkt.c:1493:SSL alert number 42:

I have postfix running on mail.myserver.com for the past 15+ years, successfully receiving and sending mail. All certs are fully valid using Let's Encrypt. I can verify that they are fine using ...
Kurt Granroth's user avatar
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1 answer
145 views

Postfix TLS: Examples for problems when using client certificates

The Postfix documentation states the following with regards to the parameter for client certificates, smtp_tls_cert_file: smtp_tls_cert_file (default: empty) [...] Do not configure client ...
hjsimpson's user avatar
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Is Certificates are required for STARTTLS connection on LDAP

My LDAP server's ldap.conf file # # LDAP Defaults # # See ldap.conf(5) for details # This file should be world readable but not world writable. BASE dc=coretesting,dc=com URI ldap://ldap....
ram ajay's user avatar
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How to (properly) force the use of SSL or STARTTLS in OpenLDAP?

I have successfully managed to configure my OpenLDAP (which is an Apple Open Directory variant, but that should not matter) to work with both, SSL (ldaps on port 636) as well as STARTTLS (on port 389)....
not2savvy's user avatar
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1 answer
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Unable to start STARTTLS in PowerMTA server

We have PowerMTA v5.5r1 installed on Ubuntu 22.04 server. When I tried to telnet localhost with 25 port I am unable to see 250-STARTTLS option. Please help which parameter or configuration needs to ...
Sachin Kadam's user avatar
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256 views

Why exim does not use TLS when sends email to remote SMTP?

Here what exim does when sends emails to gmail and other SMTP severs Received: from ns01.virtex.kz (ns1.virtex.kz. [185.141.164.16]) by mx.google.com with ESMTP id i11-...
Falseclock's user avatar
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Nginx mail proxy: tls between the proxy and the server?

When using the Nginx Mail Proxy feature to realize an SMTP proxy, there are several options available to configure (start)tls between the client and the proxy. However, it appears between the proxy ...
Arnout Engelen's user avatar
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2 answers
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PHP8 ldap_bind : Error -1 Can't contact LDAP server

I m on almalinux 8.7 with PHP8. Test ldapsearch with TLS is ok ldapsearch -H ldap://xxxx -x -ZZ /etc/pki/tls/certs/xxxx.pem -D 'xxxxx' -w 'xxxx' -b 'cn=xxx,cn=users,dc=xxx,dc=xxxx' But ldap_bind won'...
Alex Lum's user avatar
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sendmail does not issue STARTTLS when acting as a client

I'm having problems relaying to servers that whise mail is routed through mimecast. Connections are being rejected with the message: 553 This route requires encryption (TLS) - https://community....
Alien Life Form's user avatar
1 vote
1 answer
2k views

Mail server sending to postfix refusing TLS connection with "certificate expired", but it's not

Since April 30, I'm seeing errors like that in my mail log: May 1 02:27:27 afaron postfix/smtpd[2644268]: connect from r137.info.hofer.at[66.117.17.137] May 1 02:27:27 afaron postfix/smtpd[2644268]: ...
Tobias Leupold's user avatar
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1k views

Personal OpenSMTPd relay fails when using "tls-require", works fine with just "tls"

I'm currently setting up a somewhat unique personal email server using OpenSMTPd. I have a local server (Raspberry Pi) and a remote server (VPS). Emails sent to me are sent to the remote server and ...
Josey's user avatar
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Cannot get Mutt/Gmail/OAuth2 to work - cannot STARTTLS

I'm trying to get Mutt working with Gmail using OAuth2. I'm using Debian 10 and have compiled Mutt 2.2.1 with --enable-smtp. I've created my tokens. My muttrc contains: set smtp_oauth_refresh_command=&...
John Percival's user avatar
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0 answers
144 views

Can't configure SMTP encryption - postfix

I have docker-mailserver and Roundcube in containers, beside there is MySQL database for mail data and user passwords. Dovecot inside is configured to verify logging in users passwords with database. ...
pbies's user avatar
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tls negotiation failed the certificate doesn't match the host

I'm tryin to setup Gmail send-as to send email via my SMTP server over TLS and I get "tls negotiation failed the certificate doesn't match the host" ever since I renewed my lets encrypt cert....
eng3's user avatar
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1 answer
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Postfix is getting "TLS Is required, but was not offered by host"

I've searched every forum, every article, every serverfault.com post for this issue. I'm using a fresh setup of Postfix. It is managed by Virtualmin. Whenever I try to send mail via TLS, I get the ...
Ashley's user avatar
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2 votes
2 answers
694 views

TLS/SSL on http (80) with STARTTLS

I'm researching the reason why TLS/SSL is not using over HTTP. Other protocols, such as SMTP, POP3, FTP, etc can be used on SSL ports (SMTPS, POP3S, FTPS) for the first way, and the second way is to ...
deathvu's user avatar
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does SSL/TLS STARTLS full encrypt connexion for POP and IMAP

I am configuring POP and IMAP accounts in thunderbird mail client. Here are 2 options: Security: None SSL/TLS STARTLS Authentication method: Normal password Encrypted password Kerberos / GSSAPI ...
Bob5421's user avatar
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1 vote
1 answer
3k views

Using stunnel as proxy between SSL versions for SMTP with STARTTLS

I have a quite old software which doesn't support TLS 1.2. However SMTP Server only supports TLS 1.2. Now I wanted to use stunnel to connect to SMTP server and and also listening for smtp access. I ...
Hannes's user avatar
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4 votes
3 answers
8k views

Why is port 587 preferred over port 465 in SMTP?

I have recently been developing a C# client which sends emails via a SMTP server. However I have been as to what the different terms ment, like: STARTTLS/TLS/SSL... I had a faint idea of what they ...
Choppa dude's user avatar
1 vote
1 answer
177 views

Gmail failing to accept TLS

I recently set up a postfix mail server. Testing it with other domains, everything seems to work well. However, when my server tries to send messages to gmail, they are marked as spam, with the red ...
Onion's user avatar
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1 answer
912 views

Are SMTPS and IMAPS ports really deprecated?

I've read that STARTTLS command was added and intended to deprecate the SSL ports. But even major mail servers like google still use SSL ports and even don't allow us to use classic ports with ...
knight_lightning's user avatar
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1 answer
1k views

How to read an OpenSSL cipher suite list

hMailserver is an open source Window e-mail server. For incoming e-mail it supports STARTTLS with the help of OpenSSL 1.1.1. It allows configuring the cipher suites, the default is: ECDHE-RSA-AES128-...
Jeff's user avatar
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2 votes
1 answer
2k views

Postfix 3.3.1 on Centos 8 can't enable TLSv1 or TLSv1.1

I recently migrated my main mail server to a new one, the old one had been running for almost 10 years and was the production server for around 20 domains and over 40 mailboxes. Everything went well ...
moray's user avatar
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2 votes
1 answer
2k views

Getting postfix to relay SMTP/SSL/TLS to Charter/Spectrum

I'm running Postfix on Debian as an MX for a small LAN and trying to get SMTPS working with mobile.charter.net over port 587. I followed a few links off google for setting this up along with a post on ...
Nstevens's user avatar
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0 answers
2k views

NSS-LDAP not working over TLS: do_open: do_start_tls failed:stat=-1

I'm using NSS-LDAP for authentication. Without TLS, everything works fine. Once I enable TLS (StartTLS) with a self-signed certificate, which I have added to the client, NSS-LDAP won't connect to the ...
jacobz's user avatar
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-1 votes
1 answer
705 views

Outlook 2010 can receive but not send - authentication fails - Thunderbird works

After the mailserver was upgraded from CentOS6 to CentOS 7, Outlook 2010 on Windows 7 can receive email but not send, the error says authentication failed. However Mozilla Thunderbird can receive and ...
Nick W's user avatar
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1 vote
1 answer
1k views

Deny non TLS incoming mail with postfix and force certificate check

I want to deny non TLS incoming mails on my postfix server. Here is what i've done: smtpd_tls_security_level = encrypt smtpd_tls_auth_only = yes I do not really understand the difference between ...
Bob5421's user avatar
  • 429
0 votes
1 answer
38 views

Will msmtp fallback to unencrypted connections if encrypted connections fail?

My ~/.msmtprc config file says to connect to a server on port 25 with tls on and tls_starttls on. Is there a risk that, if the encrypted connection setup fails for some reason, then msmtp will ...
a3nm's user avatar
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-1 votes
1 answer
6k views

Postfix 3.4.9 SSL issues -- no shared cipher from servers using TLSv1

Edit 1: I've narrowed it down to TLSv1 that both servers listed below (no others have failed yet) are attempting to use. I'll be contacting their webmasters requesting they stop using an insecure ...
Chris B's user avatar
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0 answers
229 views

Apache and TLS mode - password in plain text in wireshark

My apache.config: LDAPTrustedMode TLS LDAPTrustedGlobalCert CERT_BASE64 /etc/pki/tls/certs/ca.cer AllowOverride None Options None #Order allow,deny #Allow from ...
overflowed's user avatar
0 votes
1 answer
1k views

TLS from unknown: No client certificate presented

We have setup a windows server virtual SMTP (under IIS6 manager). In the SMTP settings, TLS encryption is enabled, fqdn field is "sharepoint.mycompany.com". In the server's cert store "personal" ...
Mark's user avatar
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2 votes
1 answer
131 views

CentOS OpenLDAP STARTTLS wierdness

I am having a very strange problem configuring my CentOS OpenLDAP for STARTTLS. Here's what's going on. I have a bunch os scripts that I use to configure my system. I do this to document a machine's ...
Mister Rose's user avatar
2 votes
1 answer
928 views

Do any reputable mail servers require STARTTLS encryption for SMTP delivery?

Are there any large, reputable MTAs (like gmail, hotmail, icloud, etc) that will bounce mail or otherwise fail to deliver if the receiving MTA doesn't support STARTTLS? Put another way, will ...
ATLief's user avatar
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1 vote
1 answer
233 views

Postfix bounce when unable to validate TLS option

I'm using postfix as mail transfer agent on my mailgateway to send and receive emails. Because I'm communicating with sensitive information I'm using the tls options to validate the receivers mx. He ...
Nico's user avatar
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1 vote
0 answers
261 views

Server 2012 R2 SMTP service not sending mail to non TLS servers

We have SMTP virtual server on server 2012 R2 server. I have configured it to use TLS connection. We do have real sertificate etc. Everything works fine except mail that is going to mail server which ...
Timo77's user avatar
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0 votes
1 answer
718 views

Ambari sync with LDAP using StartTLS

I'm facing an issue to sync Ambari with a LDAP server using StartTLS and a self-signed certificate. Ambari server and ldap server are both running on the same machine. I've followed the steps written ...
JeremyJJ's user avatar
0 votes
1 answer
3k views

No STARTTLS with Dovecot and Postfix

I have done a lot of searching and am not finding a solution. I had to reload Mageia 6 on my email server. I am using dovecot-2.2.34-1.mga6 and postfix-3.1.6-1.mga6. Openssl is openssl-1.0.2o-1....
Robert A. Ober's user avatar
1 vote
1 answer
185 views

I'm able send email via Thunderbird, but not via my own app. The email settings are identical

I have my Postfix server. I can send email via it with no problem using Thunderbird. For smtp I have: port - 587 Normal Password STARTTLS However, I can't send an email through the same server via ...
Poddiri's user avatar
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1 vote
1 answer
634 views

Trying to make submission (587) work - Exchange 2016

I'm trying to allow the authenticated relay (Client Frontend connector) to process requests from LAN and internet, but I'm struggling so far. First, I have linked this connector to my SSL wildcard ...
Nemesis's user avatar
  • 31
3 votes
3 answers
10k views

Client did not present a certificate (Postfix)

I have postfix SMTP relay which have been configured with TLS option. Now just realized when sending email to gmail (for example) using Microsoft outlook,found out this "Client did not present a ...
David A's user avatar
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3 votes
1 answer
10k views

Postfix STARTTLS encryption before authentication

I'm trying my best to configure Postfix with STARTTLS using port 25. Now the problem is STARTTLS is not working on port 25. 250-VRFY 250-ETRN 250-XXXXXXXA 250-AUTH PLAIN LOGIN 250-...
David A's user avatar
  • 127
1 vote
1 answer
541 views

Mail server: Does /etc/mailname have to match SSL certificate CN?

I set up a web and email server on a VPS that uses apache2 with multiple virtual hosts and postfix, dovecot, and roundcube for the email server. I am getting an authentication failure when trying to ...
Dan's user avatar
  • 151
2 votes
1 answer
6k views

postfix tls not reading or finding key

I've been having issues sending mail to my server, and there are indications of TLS errors (mostly from the maillog). What I've tried: Ensuring that postfix / dovecot can read the certificates (made ...
user avatar
3 votes
1 answer
236 views

Sendmail process crashes as soon as STARTTLS is received

I just upgraded my server from FreeBSD 10.3 to 11.1. It's now running Sendmail 8.15.2 and OpenSSL 1.0.2k-freebsd 26 Jan 2017. Since the upgrade, sending mail to my server is failing. I cranked up ...
FKEinternet's user avatar
-1 votes
2 answers
2k views

Is TLS necessary for port 25 for MX delivery?

I am in the process of implementing a new Postfix implementation on an existing environment which is extremely old. While doing so I am requiring all clients to connect securely on either 465 or 587 ...
Michael Moser's user avatar
0 votes
1 answer
756 views

SMTP Server (Exchange 2003) hangs up on client after STARTTLS command after adding cert

I am stumped on this. I have Exchange Server 2003 still in use. I created a valid LetsEncrypt SSL cert, and successfully imported the pfx in my Default SMTP Virtual Server properties, Access tab. ...
Brian B's user avatar
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