NAS
A storage device connected to a network. Depending on the model and software, it can also run services such as backups or email.
Synology
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Small terms.
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From DNS to backups: find short explanations of the terms used in our articles. Search directly or browse by topic.
Explore the PTR guide →24 terms · Page 2 of 2
PTR record
Maps an IP address to a hostname. This DNS record enables reverse lookups; for a mail server it should match the mail host. The internet or hosting provider normally controls it.
DNS & networking · Email
RAID
Combines several drives into a storage arrangement. Depending on the level, it can tolerate drive failures, but it does not replace a backup.
Backup & operations
Reverse DNS
A DNS lookup that starts with an IP address and retrieves its hostname. It uses PTR records.
DNS & networking
SMTP
The protocol used to submit and transfer email between mail clients and servers or between servers.
SMTP relay
A service that accepts outgoing email from your server and delivers it onward. It can be useful when your own connection is unsuitable for direct delivery.
SPF
A DNS-based policy listing the systems allowed to send for a domain used in the SMTP envelope. SPF does not by itself verify the visible From address.
Email · Security
Read the full guide: SPF →TLS
Encrypts a network connection in transit. It protects the connection between participating systems, rather than automatically providing end-to-end email encryption.
Security
TTL
For DNS, the intended time an answer may remain cached, measured in seconds. Cached answers may remain unchanged until that period expires.
DNS & networking
Two-factor authentication
Requires two different authentication factors, such as a password and a one-time code or security key. It reduces the risk from a stolen password alone.
Security
VPN
An encrypted tunnel connecting devices or networks over another network. It can provide remote access without exposing every internal service publicly.
DNS & networking · Security
VPS
A virtual server hosted on shared physical hardware, with its own allocated resources and operating system environment. Administration responsibilities depend on the service.
Backup & operations