r/Mailbox_org

I send important private events from my private calendar to my work calendar to know when to take time off or vacation. This worked fine in the past with a gmail account. I don't want to setup my private calendar within outlook on my work laptop.

I'm slowly switching to mailbox.org and now I'm facing the following issue:

• I'm using the mailbox.org web-interface. I have a paid account, only one e-mail address and that uses the ending mailbox.org.
• I create a calendar event and invite my wife (private outlook.com account) and myself at my work e-mail address (microsoft exchange as far as I can tell)
• My wife gets a an e-mail with the invite, the invite never reaches my work e-mail, not even in the spam folder.
• I also tried the procedure using the ios calendar app setup with mailbox.org, same result.
• I tried inviting myself from my mailbox.org to my gmail adress, that works.
• So invites seem to generally work, they just don't reach my work e-mail address. This could now be a specific issue with the server settings of my company, and I can work around that somehow. But I'm worried I might have the issue with other recipients using microsoft exchange in the future as well.

Anyone have similar issues?

Inclusion in the BSI Hall of Fame 2026

Having already been awarded BSI Gold status in the 2025 Email Security Year, mailbox has once again been inducted into the Hall of Fame this year: in 2026, the Federal Office for Information Security (Bundesamt für Sicherheit in der Informationstechnik, BSI), eco, the German Association of the Internet Industry (eco, Verband der Internetwirtschaft e. V.) and Bitkom e. V. focused on the implementation of the DNSSEC email security standard.

What is DNSSEC?

DNSSEC stands for Domain Name System Security Extensions and uses cryptographic signatures to protect DNS queries against tampering and forged responses. This makes it possible to verify whether the DNS data provided for a domain actually originates from the relevant operator and has not been altered en route.

Security at mailbox

mailbox has been successfully implementing DNSSEC and other modern security standards for years, so we are all the more delighted about the independent audit and confirmation by the BSI.

Understanding and implementing email security

What exactly are DNS and DNSSEC, why is DNSSEC so important, and what should you bear in mind when using your own custom domains? Find out more in our article: https://mailbox.org/en/news/bsi-hall-of-fame-2026-DNSSEC/

SOGo (the webmail in mailcow) still has no dark mode, and the CSS themes I found tend to break after SOGo updates. So I built one that doesn't touch SOGo's stylesheets at all.

GitHub: https://github.com/Sub-7/mailcow-sogo-darkmode

What it does

• Dark mode for mail, calendar, contacts and preferences: Auto (follows your OS), Dark or Off. Toggle button in SOGo's toolbar, or Alt+Shift+D
• Your own header and accent colors, shown exactly as picked in dark mode too
• Resize folder pane, message list, header and user area by dragging the borders
• Text size per area
• Unread messages that actually stand out: bold, color bar, optional tinted background
• Settings per browser, nothing is stored on the server

Why it survives updates

It's a single JavaScript file, mounted via docker-compose.override.yml onto the js/theme.js that SOGo already loads on every page. No mailcow file is modified (git diff stays empty), so mailcow's update.sh leaves it alone. An optional post_update_hook.sh keeps the mount path in sync.

Safe to try

• Test it without touching the server: paste the file into the browser console on your SOGo page. It only affects that tab until you reload.
• Installing only restarts the SOGo container for a few seconds. Mail delivery, IMAP and SMTP are not affected.
• No network access at all: no fetch/XHR/WebSocket, no external resources, no eval, no cookies. It only stores its settings in localStorage. One unminified file, please read it before installing.
• Uninstall in three steps. A checksum confirms that SOGo serves mailcow's original file again.
• Updates via update.sh with checksum verification, backup and rollback. No auto-update.

Limitations

• HTML emails with their own colors are inverted too (images keep their normal colors).
• If you customized custom-theme.js, it won't load while this is installed.

Tested with SOGo 5.12 on my own mailcow server and in daily use. Built with the help of an AI assistant (Claude). Feedback, bug reports and translations are very welcome!