Проверка SMTP:

# date | mail -s test petrov@test.alt
# mailq
Mail queue is empty

Проверка IMAP (выход по Ctrl+D):

# openssl s_client -crlf -connect dc.test.alt:993
...
tag login petrov@test.alt Pa$$word
tag OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE
IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS THREAD=ORDEREDSUBJECT
MULTIAPPEND URL-PARTIAL CATENATE UNSELECT CHILDREN NAMESPACE UIDPLUS
LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES
WITHIN CONTEXT=SEARCH LIST-STATUS BINARY MOVE] Logged in

где dc.test.alt — имя узла сервера SOGo.