Using Microsoft power-shell command to change default mailbox size 50gb to 100gb.
First Open powershell from windows machine and type
$UserCredential = Get-Credential
Enter office 365 admin credential and stored $UserCredential variable.
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection
Import-PSSession $Session -DisableNameChecking
Set-Mailbox sukhesh@geminigroup.co -ProhibitSendQuota “99GB” -ProhibitSendReceiveQuota “98GB” -IssueWarningQuota “98GB”
Above method will fix office 365 mailbox storage limits .
After execute this command Email box size will change to 100gb.
Microsoft free to support for expand mailbox size upto 100gb.