• by Ray Schultz , February 5, 2019

Mailchimp has emailed customers to tell them that Mandrill, its email delivery API that facilitates the sending of transactional emails, is out -- and will be out indefinitely. 

The ongoing outage affects about 20% of outbound volume and a majority of inbound email and webhooks, the email says.

Resolving the issue could take “several days or longer,” it adds. Affected users will be offered refunds when the outage is over.  

Customers are facing several possible problems. “The impact to users could come in the form of not tracking opens, clicks, bounces, email sends, inbound email, webhook events, and more,” Mailchimp writes.

Mailchimp had not answered a request for comment at deadline. The service outage apparently began over the weekend. 

“Mandrill uses a sharded Postgres setup as one of our main datastores,” the email explains. “On Sunday, February 3, at 10:30pm EST, 1 of our 5 physical Postgres instances saw a significant spike in writes.”

The email continues: “The spike in writes triggered a Transaction ID Wraparound issue. When this occurs, database activity is completely halted. The database sets itself in read-only mode until offline maintenance (known as vacuuming) can occur.”

Mailchimp notes: "The database is large — running the vacuum process takes a significant amount of time and resources, and there’s no clear way to track progress."

With regard to refunds, the company states: “You don’t need to take any action at this time — we’ll share details in a follow-up email and will automatically credit your account.”

It also vows: “We’re trying everything we can to finish this process as quickly as possible.”

Mandrill users were angered when the firm began charging for the service in 2016, according to reports.