Galaxy 2 problems sending mail

[#1]

I have had real problems setting up Plusnet email on my Galaxy 2  but thanks to advice on previous posts, the settings seem right and I can now receive mail but I can't send it - it gets stuck in the outbox "sending" permanently. In the effort to sort out the original problem a helpline advisor talked me through installing K9 and a gmail address. However, the phone shop subsequently reset the phone to factory settings - wiping out K9, though when I checked the app store, it showed up that this was still registered to the device, ( but I can't find it). I still have the the gmail account on the phone and I can send mail from this account. Please can anyone advise, also re "synching" - sadly must admit to ignorance as to whether I should have done something with this. Appreciatively, an exasperated new-comer.

[#2]

I'm sorry for the delayed response,
If you're wanting to go down the route of using K9 again surely if the play store recognizes that you've used it in the past it should allow you to download it again?