2026-09-30: GitLab Email delivery to Yahoo and related providers delayed/disrupted

GitLab Email delivery to Yahoo and related providers delayed/disrupted (Severity 2)

Problem: Outbound email delivery to Yahoo and related providers is being intermittently delayed or deferred.

Impact: Verification emails and other time-sensitive security messages are being delayed for some users. Some messages are delayed rather than rejected, which can cause verification links or codes to expire before delivery.

Causes: Mailgun is returning temporary deferrals for outbound email to Yahoo and related providers, with the error indicating unexpected volume or user complaints. We have also identified that a recent spam and phishing campaign abusing the email on push feature likely drove the high outbound volume and recipient complaints.

Response strategy: We opened Mailgun support ticket #4285388, and Mailgun has acknowledged the issue and transferred it internally. We have reached out to Yahoo and have been directed to submit a ticket via senders.yahooinc.com. Trust & Safety has started auto-banning accounts associated with the campaign, and the Source Code engineering team has been notified to work on longer-term mitigations.