No response for Birthday gift

I don't think you're unreasonable to expect an acknowledgement. I do think you are unreasonable to expect an acknowledgement in such a short space of time. Maybe she's been busy at work all day, is really tired, has a headache, distracted by the needs of her family, cooking, etc, or someone dropped by or they went out to dinner. I'd give it 2-3 days before starting to think it's being dragged out a bit long at least.

How do you know she has received it? Or how does your son know she received it?

I know some email addresses allow you to get a “mail received” or “mail read” message but not all do and the recipient can change the settings to not send such messages.

If I haven't had confirmation I usually wait a day or so then send a message asking "Did your pressie arrive safely?" It seems a fair question and I don't think offence is caused.

As others have said, it has very likely gone to her Junk folder. This happens regularly to me when in receipt of correspondence from an unfamiliar contact or when I’ve sent gift certificates electronically to others. Let’s hope that’s the explanation.

How is your relationship with her? Does she normally respond quickly, or are things a bit distant?

Either way, please give her some time. She was at work when you first texted. A lot of workplaces don’t allow people to be on their personal phones unless on break. Chances are, she and your son had plans for after work to celebrate her birthday. If you haven’t heard in a week, I’d follow up to ensure it was received.

As you have a copy of the email you could forward it and then she will see it’s from you. You could also request a read report before you send it. As someone has already suggested she might not have time on her birthday to scour her junk mailbox. You can always ring your son the next day and ask him if she received it and if she liked it.

Perhaps it's gone straight to her Junk folder - or maybe she'd rather you didn't buy her any presents. We only buy for children in our family.

I would give someone 24 hours before expecting a response. She responded to your text, then spent the day at work. Maybe her husband had dinner or something else planned this evening.

I know you are anxious about her getting the email, but at least let her get through the day today.

I would feel annoyed at the lack of response, but I would let it go. She will most likely text you soon and in any case you have a full year to decide whether she merits another birthday gift!