I receive my monthly disability cheque from Sunlife of Canada through the mail. I have been told by them that I will have to wait until after the mail strike to receive any further payments unless I sign up for automatic deposit. For personal reasons I do not wish to us automatic deposit. I have contact Sunlife several times and offered to pick up the cheque or pay for a courier delivery.. I was refused on both accounts. Is this legal for them to hold back my monthly payment. Are they not responsible to ensure payment dates are met.

Thank you

They are not refusing payment, in fact they offered it though direct payment, it is you that have refused that option.
So yes while they are responsible, they made a offer to do that, but once you refuse that option, they are not required to offer other options.

In fact, they can if they wanted, make direct deposit the only option