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GetDomains

procedure GetDomains(AStrings: TStrings);

Example​

procedure ListDomains(const Addresses: TIdEMailAddressList;
  const Domains: TStrings);
begin
  Addresses.GetDomains(Domains);
  // Domains has been cleared and repopulated.
end;

Usage​

GetDomains clears a supplied strings object and fills it with first-seen unique lowercase derived domains, including an empty-domain entry.

Additional Technical Info​

GetDomains replaces a caller-supplied string collection with distinct lowercase values derived from every address item's Domain.

ParameterMeaning
AStringsBorrowed mutable output. Nil is accepted and produces no change. Non-nil output is cleared first.

For a non-nil target, the method calls BeginUpdate, clears it, then for each address computes LowerCase(Item.Domain). It uses the target's IndexOf to test uniqueness and calls Add only when absent. EndUpdate runs in a finally block.

An address without an at-sign has an empty derived domain. The empty String is therefore a legitimate emitted value (at most once), not silently skipped. Malformed multiple-at addresses contribute the suffix after the last at-sign.

Lowercasing uses Delphi SysUtils.LowerCase without an explicit invariant locale. It does not validate DNS labels, remove whitespace, trim a trailing dot, apply IDNA/Punycode or normalize Unicode. Treat results as implementation-derived grouping keys, not canonical Internet domains.

Target settings remain significant. A default unsorted TStringList preserves first-seen domain order. A sorted target can reorder additions, and its case/duplicate/comparison policy participates in IndexOf and Add. The method clears content but does not reset those settings or associated callbacks.

The operation is non-transactional. Errors or callbacks can leave a cleared or partially populated target, though update state is balanced. Source addresses are unchanged.

The loop is O(n*m) with a linear unsorted IndexOf over up to m unique domains; a sorted concrete target can use different lookup/insertion costs. Both source and target are mutable and not thread-safe.

The source-reviewed example makes the destructive output contract explicit and was not executed.

External references

Created 2026-07-15