| Price from | Free | $0.83/mo |
| Free plan | Yes | — |
| Free trial | — | Yes |
| Open source | — | — |
| Web | Yes | Yes |
| macOS | Yes | — |
| Linux | Yes | Yes |
| API | Yes | Yes |
| Self-hosted | Yes | Yes |
| Plans published | 1 | 2 |
| Spec score · Mail Server Software | 8.3 (#4) | 8.3 (#6) |
| Deployment | Citadel can run in Docker, through a Linux build script, from source, or via a hosting provider. | The Enterprise Edition is an on-premises product that keeps data on the user's own server. |
| Purpose | Citadel is an email, collaboration, groupware, and content-management system. | iRedMail is open-source software for deploying a full-featured mail server. |
| Support | Support is provided through an active user and developer community, an online knowledge base, a support forum, and a mailing list. | Enterprise Edition pricing includes technical support; general technical questions and issues can also be posted to the online forum. |