How to Compile the Zulip Desktop Client from Source on Ubuntu 16.04 (Xenial)

Building the Zulip desktop client from source on Ubuntu 16.04 LTS (Xenial Xerus) requires resolving Qt5 WebKit, multimedia, and GStreamer Phonon audio backend dependencies.

Stack: Ubuntu 16.04 LTS • Qt 5.x • CMake • Zulip Desktop 0.5.x

Build and Installation Commands

# 1. Install Qt5 development libraries and phonon GStreamer backends
sudo apt-get install git cmake qt5-default libqt5svg5-dev libqt5webkit5-dev   qtmultimedia5-dev libjson0-dev phonon-backend-gstreamer phonon4qt5-backend-gstreamer -y

# 2. Download and build Zulip Desktop
wget https://github.com/zulip/zulip-desktop/archive/0.5.1.tar.gz
tar -zxf 0.5.1.tar.gz
cd zulip-desktop-0.5.1
mkdir build && cd build
cmake .. -DBUILD_WITH_QT5=On
make
sudo make install

# 3. Register Desktop launcher
cd /usr/share/applications
sudo ln -s /usr/local/share/applications/Zulip.desktop .

[Solved] Fixing Broken DomainKeys and DKIM Signatures Sent via PHP mail()

When sending emails through PHP's native mail() function on a server configured with SPF, DomainKeys, and DKIM (such as Plesk), desktop mail clients (Outlook, Thunderbird) may sign outbound emails correctly, but emails dispatched from web scripts fail DKIM verification with invalid domain signatures.

The Trap: Setting a raw From: string inside $additional_headers causes the sendmail wrapper to misidentify the originating signing domain d=$DOMAIN.

The Problematic Call

// This breaks DKIM signatures by overriding the sender envelope incorrectly:
mail($to, $subject, $message, "From: Name <user@domain.com>");

The Solution

Explicitly pass the envelope sender using the -f flag in the 5th parameter ($additional_parameters):

// Correct invocation with verified envelope sender:
mail($to, $subject, $message, "", "-f user@domain.com");

Verification Tip: Send a test email to check-auth@verifier.port25.com. The automated robot will reply within seconds with a detailed SPF, DKIM, DomainKeys, and SpamAssassin diagnostic report.

[Solved] Postfix SASL Authentication Failure: realm changed: authentication aborted in Plesk

When enabling STARTTLS on a Plesk server running Postfix, mail clients like Mozilla Thunderbird may connect normally, while Microsoft Outlook clients repeatedly fail with authentication popups and the following mail log errors:

Environment: Plesk • Postfix with STARTTLS • Cyrus SASL Authentication

postfix/smtpd[1929]: warning: SASL authentication failure: realm changed: authentication aborted
postfix/smtpd[1929]: warning: SASL DIGEST-MD5 authentication failed: authentication failure

Root Cause & Solution

Outlook struggles with DIGEST-MD5 SASL negotiation over TLS on certain Cyrus SASL configurations. Restricting the SASL mechanism list to CRAM-MD5, PLAIN, and LOGIN resolves the negotiation conflict:

1. Edit /usr/lib64/sasl2/smtpd.conf and update mech_list:

   mech_list: CRAM-MD5 PLAIN LOGIN

2. Edit /etc/postfix/main.cf and confirm security options:

   smtpd_sasl_security_options = noanonymous

3. Restart services:

   service postfix restart
   service saslauthd restart

Setting Up Vim with Python 2/3 Support and Code Completion on Ubuntu 16.04

Configuring Vim as a fast, keyboard-driven Python IDE significantly boosts developer productivity. When following standard Vim Python configuration guides on Ubuntu 16.04 (Xenial Xerus), several key adjustments are required to achieve clean PEP 8 indentation, accurate syntax highlighting, and YouCompleteMe code autocompletion.

Stack: Ubuntu 16.04 LTS • Vim 7.4 / 8.0 • Python PEP 8 indentation rules

1. Enforcing Clean PEP 8 Indentation

Add the following configuration to your ~/.vimrc to ensure 4-space indentations, soft tabs, and trailing whitespace highlighting:

" PEP 8 standard formatting for Python buffers
augroup python_indent
    autocmd!
    autocmd FileType python setlocal tabstop=4
    autocmd FileType python setlocal softtabstop=4
    autocmd FileType python setlocal shiftwidth=4
    autocmd FileType python setlocal textwidth=79
    autocmd FileType python setlocal expandtab
    autocmd FileType python setlocal autoindent
    autocmd FileType python setlocal fileformat=unix
augroup END

2. Installing YouCompleteMe on Ubuntu 16.04

Install prerequisite development libraries before compiling the YCM C-extension:

sudo apt-get install build-essential cmake python-dev python3-dev -y
cd ~/.vim/bundle/YouCompleteMe
./install.py --clang-completer