You may or may not know, apologies if you do, but if he sees the purser or officer responsible for crew then he should be able to get a list of port agent addresses for the upcoming ports, you can then send mail to the agent addressed to 'CREW NAME, SHIP NAME, C/O AGENT....' and you can send it out straight away, honestly its well worth it. Also, if he's doing a lot of time in Alaska then it could be worth him getting a US PAYG sim card, he can text you and you can call him. Once you get a routine with his time off and acceptable hours for you, you'll be sorted :-)