Gmail users encountered error messages, high latency and other unusual behaviour at the service, according to Google.
A massive blackout on Monday temporarily disrupted popular Google services such as Gmail and video-sharing platform YouTube, derailing the remote learning, work and entertainment that people have come to rely on during the pandemic.
About 17,000 people reported Gmail service problems at a peak point at about 2:30 pm in California (4:00am IST) , where Google has its headquarters, according to the website Downdetector.
Other Google services such as YouTube, Maps, and search appeared to be operating normally.
The broad outage on Monday lasted about 45 minutes.
Services that require users to log into accounts such as YouTube or Gmail had "higher error rates" than usual, resulting in people being denied access, Google said of the Monday outage.
Google indicated on its dashboard during that outage that it involved services for "the majority of users."
Already ubiquitous, online services have become more critical this year amid the COVID-19 pandemic, as millions work from home and students take their classes online.
Disruptions to online service providers are not unusual. Amazon Web Services (AWS), the Amazon subsidiary specialising in on-demand cloud services for businesses and individuals, experienced a major technical outage in November.