theonedev/onedev · error · ExplicitException

Subject required to open issue via email

Error message

Subject required to open issue via email

What it means

When a new issue is created by sending an email to a project's issue mail address, the email subject becomes the issue title. OneDev requires a non-blank subject, and throws ExplicitException if it is missing.

Source

Thrown at server-core/src/main/java/io/onedev/server/mail/DefaultMailService.java:758

							@Nullable User submitter, ParsedEmailAddress parsedSystemAddress, 
							Collection<InternetAddress> receiverInternetAddresses) {
		String messageId = getMessageId(message);
		if (messageId != null) {
			var existingIssue = issueService.findByMessageId(messageId);
			if (existingIssue != null) {
				logger.warn("Ignored opening issue from message as issue with same message id already exists: {}", 
						existingIssue.getReference());
				return existingIssue;
			}
		}

		Issue issue = new Issue();
		issue.setProject(project);

		try {
			var subject = message.getSubject();
			if (StringUtils.isBlank(subject)) {
				throw new ExplicitException("Subject required to open issue via email");
			} else if (subject.trim().toLowerCase().startsWith("re:")) {
				throw new ExplicitException("This address is intended to open issues, " +
						"however the message looks like a reply to some other email");
			}
			issue.setTitle(subject);
		} catch (MessagingException e) {
			throw new RuntimeException(e);
		}
		
		if (messageId != null)
			issue.setMessageId(messageId);

		String description = parseBody(message, project, issue.getUUID());
		if (StringUtils.isNotBlank(description)) 
			description = stripSignature(description);
		if (StringUtils.isNotBlank(description))
			issue.setDescription(decorateContent(description));
		

View on GitHub (pinned to d44925c47c)

Solutions

1. Set a non-blank subject line before sending to the issue email address
2. If sending programmatically, set message.setSubject(...) with a non-empty value
3. If the mail is not meant to create an issue, send it elsewhere than the issue address

Example fix

// before
MimeMessage m = ...; // no subject set
// after
m.setSubject("Fix login page timeout");

if (StringUtils.isBlank(message.getSubject())) throw new IllegalArgumentException("Subject required");

try { issueService.openViaEmail(message); } catch (ExplicitException e) { bounce(e.getMessage()); }

When it happens

Trigger: Sending an email with an empty or whitespace-only subject line to a project issue-creation email address.

Common situations: Composing a fresh email and leaving subject blank; some mail clients send subject-less mails for quick notes; automated systems generating emails without subjects.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• This address is intended to open issues, however the message
• Title is required
• Issue ${issueReference} is not in current project
• Invalid issue id/number
• Not eligible for multi-value

AI-assisted analysis of theonedev/onedev@d44925c47c (2026-09-06). Data as JSON: /api/errors/9328e8d452dd870b. Report an issue: GitHub.