What are you seeing which makes you think that a timeout is too short?
To be honest all I have to go on is the behaviour I'm seeing and a search for similar problems elsewhere. In some of those cases the problem has been fixed by changing the timeout, and as my first post didn't prompt any suggestions I decided that trying that change might be a good start.
The behaviour I am seeing is that I am receiving duplicate copies of emails over a number of days. The worst offender is a rather lengthy daily newsletter that I subscribe to, and I receive copies of it for about three days. A single copy of each of the last three days emails will arrive simultaneously a few times a day, as if they had all been retried following a delivery failure. Some other random emails have given the same behaviour, but none of them have had the same number of duplicates.
As I said in my first post I'm open to any suggestions of where to look and what to look for.