We are having an issue with mobile users not receiving emails that have attachments when working from home on Wi-Fi. Email without attachments are received without issue.
When users return to office and connect to wired network connection, all emails are received (including the ones with attachments that did not come in the day before when working from home on Wi-Fi).
The users are connected to office network through Sonic Wall Global VPN Client to access files and folders on servers, but email is hosted using Office 365 Business Essentials, email only. VPN is not required for them to access email. Outlook 2010 and 2013 on users laptops.
Any help is appreciated.