Question

What are special test messages consisting of empty envelopes?

Answer 1

SMS language, textspeak or texting language is the abbreviated language and slang commonly used with mobile phone text messaging, or other Internet-based communication such as email .... Initialisations (acronyms and abbreviations composed of initials); Reductions and shortenings, and omission of parts of speech.

Answer 2

probes. A probe is an SMTP session that does not deliver mail.