You need to understand the context of the regulation, not what you find elsewhere. The reference to "by mail or telephone, when the check is mailed to the depositor" is referring to cases in which the depositor calls or mails in a request that funds be withdrawn from the [savings or MMDA] account and that the bank send the proceeds of the withdrawal to the depositor by bank check.
It has nothing to do with writing a check on an MMDA and depositing that check in another bank. For the record, I am among those that would consider such a transfer (to the third party bank) a 3/month transaction.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8