The fact that this is being done in a poly relationship aside, I find it odd that a partner would put a 'requirement' to be texted or contacted every evening on the other partner, as a mandatory requirement. Think about it...if this was being done in a mono relationship, wouldnt it be strange to have a partner say 'I NEED you to text me every evening'? (As opposed to 'I really enjoy talking with you of an evening, I'd like us to do that if and when we can').
What emotional need does this boyfriend have, which he cannot fulfill himself, which requires a text from your wife every evening? He sounds insecure and needy, like he doesn't trust that he will get sweet texts from your wife often enough unless he puts a rule on it. That sort of thing makes a relationship far less organic, in my opinion.
I can understand 'mandatory' rules (or rather, boundaries - 'I require myself to only be in relationships where partners do XYZ') on things like safe sex, honesty, or even requiring certain check in or care after a partner has gone on a date (especially if it's a first time date, or just opening up a relationship, or first time sex with new partner etc). But every night? That's a bit much.
But...all of that aside...
Your wife gets to decide who she dates. If she wants to date insecure and needy, then she gets to do that.what you get to do, is set a boundary of 'I will not be with someone who allows their other relationships to infringe on *our* intimacy'. That way, it is the way your wife's behaviour is impacting on you that you focus on communicating, rather than the fact she's decided to date a guy with freaky rules.
So consider communicating to your wife that the fact that she's texting this guy, right before your bedtime together, infringes on your intimacy. Consider what kind of things you need with your wife before bed, to set up an intimate space or atmosphere for the two of you. I completely get it, by the way. When I've had a partner, bedtime is one of my favourite things to do with them - the settling down, the snuggling, talking, love making. It's really a very intimate time and I would also be annoyed if something distracted from that intimacy. To me, it would be the same as if a partner of my partner asked them to text just as he and I were about to have sex, or about to have a serious talk, or about to massage each other. I would be thinking, "no, this is one of our special times where there is a zone of intimacy just for us, you don't get to infringe on that". Similarly, I'm sure you wouldn't ask your wife to text you just as she was sitting down at an intimate dinner with boyfriend or some such. The split in focus ruins the atmosphere.
Perhaps putting it as "I need to be in relationships where all my partners (whether your wife or girlfriend or others) respect my intimate time with other partners, and don't try to take my focus off those" would be a good way to communicate it to your wife, along with explaining that, for you, bed time is one of those intimate times. You could figure out when 'bed time' starts for you, such as - is it when you go upstairs to the bedroom? Is it when you have both used the bathroom? And then explain that after that 'marker' in time begins, you need focus for just the two of you. You and your wife may not have realised the intimacy you put on this time before, because until now, no one has tried to interfere with it, but I would be explaining it as an intimate time for the two of you, just like love making or a romantic dinner or (any other, intimate things you do together) - and that you have a need for that to be respected. In the same way, you could explain you would not be interfering with her intimacy with boyfriend if she and he were having alone time together - such as, if she was at a sleepover or romantic dinner with him.