I write reception reports - 1559 ship QSLs and 70 landbased QSLs in DSC so far...
I write personal letters and I don't use any standard form letters. Write some short words about you like profession, age, city you live in, that your hobby is shortwave-listening and that you like to collect verification from ships/stations that you had received. All together in 3 to 4 sentences. People don't have time to read a 4 page letter in this times.
Don't use SINPO or SINFO - they do not know what it is. Write if the signalstrength was good/medium/weak, and if there was some fading and atmospheric noise on the QRG and that you have had no or little problems to receive the station.
Important: mention you email address beside your physical address. Sometimes you will get an answer via email. That's short and efficiently.
In 99,9 per cent I send letters by postal ways and no email. I think that most emails went directly into the spam folder.
I don't include postage - just a self-addressed-envelope. Writing to german stations, I enclose a self-addressed-and-stamped-envelope.
Mention your receiver, antenna and decoding software (mulitpsk e.g.). 2-3 Sentences are enough.
For the reception details, copy the received message into your report like:
(MF=2.1875 MHz) <Selective call to a particular individual station>
Called MMSI station address: 002442000 [Coast station: Netherland CG Radio] (Netherlands)
MMSI self-identifier: 311513000 SEVEN SEAS VOYAGER - C6SW3
Telecommand 1: Test
Telecommand 2: No information
Neither RX/TX frequencies nor position supplied
Check Sum: OK
Date and time of decoding: 03/10/2016 06:47:25
Return rate from ships is slightly under 40 per cent. So 4 answers from 10 letters send...could be less.
Hope this helps. If you have any further questions, I'm here :-)
vy 73, Andy - DL1DXX