Side by side
Citadel vs Kolab
Both stand on mail server software. Which one you can start free with, which one lets you read the code, and what each costs once you pay.
Free plan APILinuxMac+2
Visit Citadel 
Free plan AndroidAPIiPhone+5
Visit Kolab The facts
| Citadel | Kolab | |
|---|---|---|
| Free plan | Yes | Yes |
| Open source | Not published | Not published |
| Runs on | API, Linux, Mac, Self-hosted, Web | Android, API, iPhone, Linux, Mac, Self-hosted, Web, Windows |
| Lowest paid plan | Free or on request | Free or on request |
| Plans published | 1 | 1 |
| Maker | Not published | Not published |
| Website | citadel.org | kolab.org |
| On mail server software | #3 of 34 | #7 of 34 |
Alternatives to Citadel Alternatives to Kolab The whole list