You can increase the Time Out request by going to
Tools-->Accounts-->(Your account)-->Properties-->Advanced Tab-->Time
Out-->Increase it from 1 Minute to 2.30 Minutes.
May you please copy and paste the exact error msg.

Usually, the best way if to log on using webmail instead of Windows Mail
when this happens.  Not all email providers offer that, though.

Thanks robertmiles!

the 'massive' email may have finally downloaded in the time i spent asking
for help.  I followed your advice about webmail.  tried moving my address out
of the secondary mail box back to the primary one. I don't know if this
jiggled it a bit or just kept me busy whilst it downloaded.
such a prompt reply to my query - thank you eversomuch.