Skip to main content

IsEmailValid

Function IsEmailValid( const aValue : string) : boolean

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := IsEmailValid('integration@example.invalid');  // True
end;

Usage​

IsEmailValid checks whether a string matches Velox's anchored email-like regular-expression pattern.

Parameters

NameTypeDescription
aValuestring, constComplete text to test. Velox does not trim or otherwise normalise it before matching.

Returns

True when aValue matches the fixed pattern; otherwise False. A true result says nothing about deliverability.

Behaviour

  • Both sides of @ must start with one or more regex word characters.
  • After that initial run, a dot, hyphen or underscore is accepted only when followed by another non-empty run of word characters.
  • The domain does not have to contain a dot or a conventional top-level domain. For example, user@host matches.
  • The same punctuation rules are applied to the local and domain portions. This means an underscore in a domain label can match even though it is not a conventional DNS host-name character.
  • The helper performs no case conversion, DNS lookup, mailbox verification or SMTP interaction.

Errors

The pattern is a fixed, valid product constant, so ordinary non-matching input returns False. Exceptions from allocation or the installed regular-expression engine are not caught by the Velox function and would propagate to the script.

Usage notes

Use this helper only for the deliberately narrow syntax policy described above. If a Flow requires an organisation-specific address policy, enforce that policy explicitly and treat actual delivery success as a separate SMTP outcome.

Additional Technical Info​

IsEmailValid applies Velox's fixed email-like regular expression to the supplied string. It is a syntactic screening helper, not proof that the address, domain or mailbox exists and not a complete implementation of the Internet email-address standards.

The example uses the reserved .invalid top-level domain. It demonstrates pattern matching only and does not contact DNS, SMTP or any other service. The example is source-reviewed and was not executed by the documentation workflow.

Implementation

The scripting import registers the Velox-owned IsEmailValid function. It passes this fixed pattern and aValue to the shared RegExMatch helper:

^(\w+([\-\_\.]\w+)*)@(\w+([\.\-\_]\w+)*)$

RegExMatch calls the two-string class overload of Delphi System.RegularExpressions.TRegEx.IsMatch, with the email text as Input and the fixed expression as Pattern. The installed Delphi routine creates a regular-expression record with its default options, performs one match and returns TMatch.Success.

Edge cases and quirks

  • Ordinary leading or trailing spaces and tabs fail because Velox does not trim aValue. Do not treat the final $ as a strict end-of-buffer assertion, however: under the installed PCRE-compatible anchor rules it can match before a permitted final newline.
  • Empty components, leading/trailing separators and consecutive dots or hyphens fail under the grouped pattern.
  • Common valid email forms that use a plus tag, quoted local part, address literal, comment or display name fail. For example, user+tag@example.invalid does not match.
  • The meaning of \w, anchors and other regex constructs is the installed Delphi PCRE wrapper's meaning. Velox supplies no regex options of its own and does not claim RFC mailbox equivalence.
  • A matching .invalid address remains deliberately undeliverable. Conversely, a matching real-looking address may not exist.
  • The three SendEmail* helpers do not call IsEmailValid; scripts must decide separately whether and how to validate recipient inputs.

Side effects

None. The function does not mutate its input or perform external I/O.

Performance and concurrency

Each call creates and evaluates a new Delphi regular-expression instance; Velox does not cache a compiled pattern. Work and temporary allocation grow with the input length. The call has no Velox shared mutable state and is re-entrant for independent inputs.

Related entries

  • SendEmailCC accepts recipient strings but does not invoke this validation helper.
  • SendEmailTo sends through the configured default sender and likewise performs no IsEmailValid pre-check.

External references

Created 2026-07-15