SMTP – Checks

Ouch, I thought with the last post to conclude the SMTP series, but I forgot one element: how to check these services, if they are operating like they should. The anti-spam triangle, how I myself decided to call it, consists of DMARC, SPF and DKIM,as I’ve covered in the previous post. Now a few simple…

Continue Reading

SMTP – DKIM DirectAdmin with Exim 4

So we had these awesome DirectAdmin posts, although I do not like DirectAdmin one little bit, which got me started with the SMTP posts, this being the last one about DKIM. After getting this cool mechanism configured on Postfix with and without Rspamd, this time we’ll be configuring it on a DirectAdmin enabled server with…

Continue Reading

SMTP – DKIM with Postfix

The first email server I’ve configured with DKIM was a Postfix server with Rspamd, hence the previous post about this. But soon I also needed this cool mechanism configured on a server with postfix only and no Rspamd involved.It needs some more work I guess, but following this guide will get you there. I’ll make…

Continue Reading

SMTP – DKIM Postfix with Rspamd

After a few easy ones (DMARC and SPF), we now have the last one in our anti-spam triangle, DKIM, which is more complicated to setup. This mechanism is probably also the most reliable and hack proof solution, since you need to configure your email server, your DNS records and combine the two to make it…

Continue Reading

SMTP – SPF

After DMARC, the next in the spam fighting triangle (DKIM being the third) is SPF. A SPF record (Sender Policy Framework) was originally to help the fight against SPAM but quickly became obsolete. Nevertheless we still need it for most providers like Gmail and Outlook.com. So, although its kind of useless, we still need to…

Continue Reading

SMTP – DMARC

Following up on the first SMTP post, this next one is probably easiest: the DMARC record. Getting it active on your domain can take a few seconds and maybe a more complicated setup a few minutes. As simple as this mechanism is to set up, it’s always has been pretty solid against the abuse of…

Continue Reading

SMTP – Backscatter check

I will dedicate the next couple of posts on a few on these mechanisms and checks. The first is to check for Backscatter. Backscatter is when a NDR (Non Delivery Report) or bounce message contain the full body of a mail / spam message. After the recent DirectAdmin posts there was a lot to do…

Continue Reading

Nextcloud 12 migration guide

Following one of the better decisions a couple of days ago, it was time today to re-install my webserver that runs Nextcloud. I made some errors setting it up, now almost a year ago. A couple of things could be fixed, a couple of things I’d rather not and just build it from the ground…

Continue Reading

New Zimbra 8.7.11 server migration guide

In the past I haven’t been so kind about the Zimbra Open Source Suite. Installing it in my own, configuring it, getting all my data to it and using it daily wasn’t a breeze. I found it especially difficult to keep it stable while ensuring security. I’ve also been somewhat active at the forums and…

Continue Reading

IPv6 on CentOS 6 and CentOS 7.4 VPS

For almost 20 years I’m working in IT and I hear “we’re running our of IPv4 addresses” and “IP version 6 is coming”. Although this is the truth, there are still not a lot of situations I come across that I need an IPv6 address. And then there was this situation where I very recently…

Continue Reading

Addendum OSI model / PDUs

I would  like to make a small addendum to my previous post about the OSI model and PDUs. What was named quickly in the Network+ videos was what protocols actually function on which layers, which I found interesting. So let me enrich you with a few examples! To clarify a little bit, after mentioning the…

Continue Reading

OSI model and PDUs

Two concepts from my Network+ study: the OSI model and PDU. OSI stands for Open Systems Interconnect and is used as a conceptual model to ease data transmission and communication. Read more about it here and here. PDU stands for Protocol Data Unit and describes the unit that is being used on a particular layer…

Continue Reading

CentOS 7 FTP server setup

I needed FTP access to my VPS since there was a WordPress update and I didn’t feel like it to do it manually: FTP / SFTP / SCP to your server and do the update from there. Fortunately installing and configuring it is easy. After configuration you can immediately login with an admin user that…

Continue Reading

CentOS 7 – Zimbra 8.7.4_GA change ssh portnumber

So, with the fresh certificate in the pocket, we’ll be going for new adventures. The first one being Zimbra, my initial choice for a collaboration suite. Email, calendar, contacts and tasks will be my main purpose for this suite. I’m installing the suite (yesterday and today…) and am stumbling upon A LOT of problems. Problems…

Continue Reading