PRTG – Error – Connecting to IMAP Server: [ALERT] Please log in via your web browser: https://support.google.com/mail/accounts/answer/78754 (Failure)

Error when using IMAP Roundtrip sensor.

Cause: Port 465 or 587 closed

Solution:

1) Need to open this port

Port for SSL: 465
Port for TLS/STARTTLS: 587

or

2) Turn ON setting “Allow less secure apps” dalam GMail Account

Refer: https://support.google.com/mail/answer/7126229?visit_id=1-636271485504237731-3787438172&rd=2#cantsignin