Originally Posted by Goucham
Do you see the same thing happen on different networks? e.g. The WiFi at work vs. the WiFi at home. Does the same thing happen when your tablets are operating in WiFi mode? The reason why I ask is that the ports required for IMAP/POP3 are sometimes blocked on a corporate network. Less so with your home connection but ISPs do routinely block standard ports for sending messages.
If it is port blocking, most email providers now offer either secure connections or alternate ports you can use. The default mail client can be made to work with the non-standard ports but you'll have to change some things in the manual setup section.
I notice this a home yesterday. I have tried on different networks. To make things clear it is only my Samsung Galaxy Player that is have this issue. My Tablets on all only WiFi as with my SGP. I will check the ISP angle.