Category: Email

Office 365 Anti-Spam IP Delist Portal

August 14, 2018 The Geek Decoder Leave a comment Email, Office 365

If you’re trying to send mail to an Office 365 recipient and the mail has been rejected because of your sending IP address, follow these steps to submit a delisting request.

Error messages may be similar to the following:

ECDHE-RSA-AES256-SHA384:256 CV=yes: SMTP error from remote mail server after RCPT TO:: 550 5.7.606 Access denied, banned sending IP [xxx.xx.xxx.xxx]. To request removal from this list please visit https://sender.office.com/ and follow the directions. For more information please go to http://go.microsoft.com/fwlink/?LinkID=526655 (AS16012609) [HE1EUR01FT043.eop-EUR01.prod.protection.outlook.com]

Check Mail Port Connections with netstat

March 14, 2018 The Geek Decoder Leave a comment Administration, Email, Security

A good way to check the connectons to mail ports is to use netstat:

# netstat -anp | grep :25
tcp        0      0 0.0.0.0:25              0.0.0.0:*               LISTEN      2170/master
tcp6       0      0 :::25                   :::*                    LISTEN      2170/master

# netstat -anp | grep :465
tcp        0      0 0.0.0.0:465             0.0.0.0:*               LISTEN      2170/master
tcp6       0      0 :::465                  :::*                    LISTEN      2170/master

# netstat -anp | grep :587
tcp        0      0 0.0.0.0:587             0.0.0.0:*               LISTEN      2170/master
tcp6       0      0 :::587                  :::*                    LISTEN      2170/master

Adding DKIM to Postfix

July 19, 2017 The Geek Decoder Leave a comment Email

DKIM on Postfix:

https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-dkim-with-postfix-on-debian-wheezy

The configuration can be tested by sending an empty email to check-auth@verifier.port25.com and a reply will be received. If everything works correctly you should see DKIM check: pass under Summary of Results.

==========================================================
Summary of Results
==========================================================
SPF check: pass
DomainKeys check: neutral
DKIM check: pass
Sender-ID check: pass
SpamAssassin check: ham
Alternatively, you can send a message to a Gmail address that you control, view the received email’s headers in your Gmail inbox, dkim=pass should be present in the Authentication-Results header field.

Authentication-Results: mx.google.com;
spf=pass (google.com: domain of contact@example.com designates — as permitted sender) smtp.mail=contact@example.com;
dkim=pass header.i=@example.com;

Email Administration for Postfix , Plesk and Qmail

October 20, 2015 The Geek Decoder Leave a comment Administration, Email

Basics
rDNS (Reverse DNS)

The Reverse DNS for an IP should be set to the EHLO value that is sent in the outgoing mail header. This is generally the HostName of the computer.

This value should also match the outgoing IP address used to send the mail.

On a multi-IP server, if the sending IP does not match the EHLO domain, you may be sending from Postfix. Switching to Qmail may cause the sending IP to match the primary IP on the server, which should correct any mis-matched IP/EHLO issues.

Read More

DMARC

October 1, 2015 The Geek Decoder Leave a comment DNS, Email

Amazonon DMARC (http://sesblog.amazon.com/post/Tx22ZELXSSZRYZR/What-is-DMARC-and-should-you-use-it).

This Google article is also helpful: https://support.google.com/a/answer/2466563?hl=en

If you scroll down to the ‘Example records’ section, you’ll see a number of examples on how to write the TXT record. Here’s an example of that record:

_dmarc.advancedmediawebs.com. 3600 IN TXT “v=DMARC1; p=quarantine; pct=5; rua=mailto:mark@domain.com”

Change IP route for Blacklist

February 12, 2015 The Geek Decoder Leave a comment Email, Iptables

Add the clean IP to the server.

Edit the firewall to NAT all connections FROM port 25 to use the new IP.

# iptables -t nat -A POSTROUTING -p tcp --dport 25 -j SNAT --to-source NEW.IPA.DDR.ESS
# service iptables save

Ensure that the IP is on eth1
or…

# iptables -t nat -A POSTROUTING -o eth1 -p tcp -j SNAP --dport 25 --to-source 123.45.6.7

SSL for Mail Server Plesk

January 13, 2015 The Geek Decoder Leave a comment Email, Plesk

Normally, checking mail may produce an SSL error for plesk mail services. All clients Outlook, Mac mail, thunderbird, show a a message for ssl certificate. How to fix it.

You would need to purchase a SSL certificate for your servers hostname and set it up so it gets used for the mail service on the server. if you try and use mail.domain.com, it’ll still give an error.

Ref: http://kb.sp.parallels.com/en/1062

Is SpamAssassin Working

December 6, 2014 The Geek Decoder Leave a comment Email, Spam

Check the header of an email


X-Spam-Status: No, score=0.1
X-Spam-Score: 1
X-Spam-Bar: /
X-Ham-Report: Spam detection software, running on the system "server.domain.com", has
identified this incoming email as possible spam. The original message
has been attached to this so you can view it (if it isn't spam) or label
similar future email. If you have any questions, see
root\@localhost for details.

You can also add Barracuda RBL to Exim in WHM

For cPanel /home/username/.spamassassin/user_prefs as described:

Other Resources:

Improving SpamAssassin accuracy on cPanel (or any other) mail servers – with statistics

IMAP and POP Email Settings

November 5, 2014 The Geek Decoder Leave a comment Email, Plesk

For a plesk server

IMAP

Incomming server
Server: mail.domain.com
Connection security: none
Authentication: Password, transmitted insecurely
User Name: user@domain.com
Port: 143

Outgoing Server:
Server: mail.domain.com
Connection security: STARTTLS
Authentication: Encrypted password
User Name: user@domain.com
Incomming: Port 587

POP

Incomming server
Server: mail.domain.com
Connection security: STARTTLS
Authentication: Encrypted Password
User Name: user@domain.com
Port: 110

Outgoing Server:
Server: mail.domain.com
Connection security: STARTTLS
Authentication: Normal Password
User Name: user@domain.com
Incomming: Port 587