The time required to
import IMAP emails to Office 365 for large mailboxes depends on several factors, so there is no fixed duration. Typically, migration can take anywhere from a few hours to several days. Key factors include mailbox size, number of user accounts, internet bandwidth, server speed, and throttling limits imposed by Office 365.
For example, a mailbox of 10–20 GB may take several hours, while larger mailboxes (50 GB or more) can take a day or longer. Network stability and latency also play a major role in determining the speed of data transfer. Additionally, Microsoft applies migration throttling to maintain service performance, which can slow down the process during peak times.
Using a reliable
MacGater IMAP backup tool can significantly optimize the process by enabling batch migration, filtering data, and reducing duplicates. Proper planning, such as migrating during off-peak hours, can further minimize delays and ensure a smoother transition.
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