Making alphabetical listing the only available sorting order is, in the context of domains, a bad design choice. Domain owners think in terms of expiry date, in terms of “How many of these damn domains are coming up for renewal soon?”.
The majority of your users will transfer domains to you as and when they are due to expire at their current registrar, probably in monthly batches. That is simply how most people operate, putting off an expense until it is due.
If you are not going to make your columns sortable, please order them by expiry date.
Sorting by expiry date would also completely solve the ongoing problem of your transfer system being limited to 245 domains (up from the previous limit of 20 domains). As described in that post, the alphabetical sorting is screwy anyway, starting at the letter D in my case.
Sorting by expiry date would also make the choice to force users to manually deselect domains from the list less frustrating - if all the domains I want to transfer are clustered at the top of the list (because they are all due to expire soon), it is relatively easy for me to then remove all the domains that appears below them.