Yahoo Blocking E-Mails from Safe Sender

[CLarner]

Since last Friday Yahoo seem to be blocking certain e-mails from a safe sender (a local theatre). I am receiving marketing e-mails and e-mails from individual staff but not ticket confirmations/bookings. 

I have added their e-mail address to my Contacts so now firmly a safe sender;  have set up a filter saying all e-mails from that address should go to my Inbox; have checked they are not going into Spam; have checked they are not on the Blocked Sender list and am now at a loss. The theatre have checked at their end and said that they cannot see any issues so it must be an issue with my e-mail.

I don't want to have to set up another e-mail address simply for theatre tickets to come through to so does anyone have any fixes other than those tried?

Many thanks in advance. 

[Mark39]

Which domain are the blocked emails coming from?

[jayach]

Also, have you asked if the senders are getting a "undelivered" report, and if so what does it say?

[CLarner]

The e-mail address is coming from The Lowry theatre in Salford so is a noreply at lowry.com e-mail.

The Lowry don't appear to be seeing any issues at their end and certainly not getting undelivered so the e-mails seem to be simply going into the ether or no man's land!