1.cypht-org / cyphtCypht: Lightweight Open Source webmail aggregator [PHP, JS]. Supports IMAP/SMTP, JMAP and EWS (Exchange Web Services)phpwebmailwebmail-clientimappop3smtp+6 morePHPLGPL-2.11.8K total256 forks+16 starsfrom 1,771 · score 2.83
2.EGroupware / egroupwareWeb based groupware server written in PHP, forum at https://help.egroupware.org/egroupwarewebmailproject-managementaddress-bookcalendarcaldav-server+4 morePHPOther license301 total115 forks+2 starsfrom 299 · score 1.10