I noticed the following alert on the USPS website:
Most mail services to Guatemala have been temporarily suspended. Until further notice, only Global Express Guaranteed (GXG) service is available… The Postal Service will, upon request, refund postage and fees on mail returned due to the suspension of service, or the sender may remail them with the existing postage once service to Guatemala has been restored. When remailing under this option, customers must cross out the markings "Mail Service Suspended — Return to Sender."
This is a global disruption, as described here:
The suspension is due to a contract dispute between the Guatemalan government and the country's postal agency, El Correo de Guatemala.
I have an interest in auxiliary postal markings. I was curious what a mailpiece returned to the USA would look like, so I sent a test cover to the U.S. embassy address in Guatemala City on September 23, 2018:
Intriguingly, it took a full sixteen days to return to my mailbox, which suggests that it might have made it to the port of entry before being turned back.
I would be interested to see scans of returned covers bearing other markings or returned to other countries.