Issue with change of contact.

I have a frustrating issue with an email contact.

Initially I inadvertantly put an email address mthornley@acb.uk.com

After receiving messages that these emails were being rejected I realised I missed a letter and the email should be mthornly@ascb.uk.com.

I deleted the incorrect version and resubmitted the newer correct version.

Despite this when I send an email to this person (which is fairly frequent) it still sends to the incorrect one.

I have looked in the contacts and the old email is not shown but it still sends to this,. I have to check when sending that the two versions shown I select the correct one.

How can I remove the incorrect email please ?

Thamk you