This is the 15319th most frequent Russian word.
поступают
"Act," "arrive," or "apply," depending on context.
In this context, 'поступают' means 'enroll' or 'enter as a student'.
Студенты поступают в университет осенью.
Students enroll in the university in the fall.
Here, 'поступают' means 'are received' or 'arrive' referring to the reception of messages.
Иногда сообщения поступают с задержкой.
Sometimes messages are received with a delay.
In this case, 'поступают' means 'act' or 'behave' when describing how someone conducts themselves.