Reference

Appenders
AppenderDbi	Log to databases via DBI
AppenderDt	Log to an in-memory data.table
AppenderElasticSearch	Log to ElasticSearch
AppenderGmail	Send emails via the Gmail REST API
AppenderSendmail	Send emails via sendmailR
AppenderPushbullet	Send push-notifications via RPushbullet
AppenderSyslog	Log to the POSIX system log
Other functions and classes
LayoutDbi LayoutSqlite LayoutRjdbc LayoutRjdbcDb2 LayoutDb2 LayoutMySql LayoutPostgres	Format log events for output to databases
LayoutElasticSearch	Format log events for output to ElasticSearch
Serializer SerializerJson	Serializers
select_dbi_layout()	Automatically select appropriate layout for logging to a database
unpack_json_cols()	Unserialize data frame columns that contain JSON
Abstract classes For developers only
AppenderDigest	Abstract class for digests (multi-log message notifications)
AppenderMail	Abstract class for email Appenders