| Price from | Free | — |
| Free plan | Yes | — |
| Free trial | — | — |
| Open source | — | — |
| Web | Yes | — |
| Windows | Yes | — |
| macOS | Yes | Yes |
| Linux | Yes | Yes |
| iOS | Yes | — |
| Android | Yes | — |
| API | Yes | — |
| Self-hosted | Yes | Yes |
| Plans published | 1 | 0 |
| Spec score · Mail Server Software | 8.0 (#11) | 7.2 (#30) |
| Deployment | Kolab is packaged as containers that can run on one host or be distributed across a larger environment. | Postfix is built from source and runs on UNIX-like systems; operating-system and appliance vendors also distribute ready-to-run versions. |
| Intended users | Kolab describes itself as a solution for companies and families that need to work and communicate together while retaining control over their data. | The project describes postfix-users as a forum for people using Postfix and postfix-devel as a list for those designing, implementing, or maintaining its source code. |
| Product | Kolab is a free and open-source communication and collaboration solution that can be run on your own infrastructure. | Postfix is Wietse Venema’s mail server, created as an alternative to Sendmail. |
