We are more forgiving of sloppy e-mails when we know they were sent from a smartphone:

When the message had correct spelling, grammar and punctuation, the sender was rated as being very credible — and there was little difference between whether the email seemed to have been composed on a computer or a phone. But when the message had errors in it, things changed: Students attributed higher credibility to the person who’d written the lousy message on a phone.

(Hat tip: J.K. Trotter)