fix(email): test saved SMTP config and add TLS modes (#3388)

packages/constants/src/SmtpConstants.ts

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import type {ValueOf} from '@fluxer/constants/src/ValueOf';
+
+export const SmtpTlsModes = {
+	IMPLICIT: 'implicit',
+	STARTTLS: 'starttls',
+	OPPORTUNISTIC: 'opportunistic',
+	NONE: 'none',
+} as const;
+
+export type SmtpTlsMode = ValueOf<typeof SmtpTlsModes>;
+
+const SMTP_IMPLICIT_TLS_PORT = 465;
+
+export function resolveSmtpTlsMode(mode: SmtpTlsMode | null | undefined, port: number): SmtpTlsMode {
+	if (mode) return mode;
+	return port === SMTP_IMPLICIT_TLS_PORT ? SmtpTlsModes.IMPLICIT : SmtpTlsModes.STARTTLS;
+}
+
+export function smtpTlsModeFromSecure(secure: boolean | null | undefined): SmtpTlsMode | null {
+	if (secure == null) return null;
+	return secure ? SmtpTlsModes.IMPLICIT : SmtpTlsModes.OPPORTUNISTIC;
+}