The IRS released a Quick Alert titled, “Extended Maintenance Window for both MeF ATS and Production Environments”.
“The MeF maintenance build window is being extended on Sunday, March 18, 2018. Both ATS and Production systems will be unavailable from 12:00 a.m. until 11:00 a.m. Eastern. The build will deploy critical system updates.
Thank you in advance for refraining from accessing the MeF Systems during this period.”
This means that any returns e-filed on Sunday, March 18th from 12am-11am ET will not be transmitted to the IRS until after their maintenance window has closed.