Because of the self sufficiency rule, you'll be hard pressed to find any FHA options that'll work on a triplex or quad. 

It very well might be the case that if the appraisal deficiency tanking your ability to close is a reason that you forfeit your deposit, or it may be the case that your lender's letter is sufficient to get you out under your financing contingency.

Keep in mind - the property still needs to cash flow for your own purposes outside of the self sufficiency test - but if you've been trying to find a way to get involved without a large down payment this is definitely a game changer. 

So would emailing them this notice be sufficient?

This might be what we do if we cannot find a tenant in a sufficient amount of time.

My plans are always perfect and the only reason they don't work out is because nobody is sufficiently motivated to carry them out to perfection. 

This in itself will not end up being sufficient if they are wrong even 1 out of 100 times.  

During diligence and appraisal I had to challenge the appraiser to adjust rents in order to pass self sufficiency test.

Ideally lenders want to see you in a job for 2 years to ensure your credit worthiness but if you can produce a (or a few) pay stubs proving your income and have sufficient reserves, you should be fine.

Technically, if you add enough chlorine/Bromine, the water will be sufficiently sanitized, I.e., germs are dead.