Resignation letter without notice period

Dear Sir/Mam,

This email is to notify you that I am resigning my position with [Comapany name] due to suffering from jaundice which will require extended treatment and recovery, and I am unsure that my ability to perform the duties of my present position will return.

I apologize for the inconvenience that I may be causing to [Comapany name], but I think it is the right thing to do at this moment of time. I want to thank you for all the support and encouragement you have always given me.

Again, it has been a pleasure working with you and I want to wish everyone at [Comapany name] the best of luck for the future.

Your's sincerely
[Your name]

Mail after an interview

Dear Sir,Mam,

I am writing to thank you for taking the time to interview me on [DATE] and to confirm my interest in the [NAME OF POSITION] job.

I was really impressed with the company and the job and, as I explained in the interview, I think I’d be well suited to the role.

[At this stage you could do a few bullet points to show the key skills you have that fit the job]
I look forward to hearing from you once you reach a decision. In the meantime, if you have any questions for me at all please do not hesitate to call me on [YOUR NUMBER].
Kind regards,
[YOUR NAME]