Old Mutual do not know how to send or receive e-mails

I received 2 sms's from Old Mutual advising that they failed to deliver messages to my e-mail address which is incorrect, yet the e-mail address quoted on the sms's is my correct e-mail address!

I sent an e-mail to *** to query the sms's and received an undelivered message advising that the mailbox is full. How does Old Mutual expect their clients to make contact with them?

Hence I do not know what messages Old Mutual was trying to e-mail me and there seems to be no way of finding out. Perhaps it's time to move my business to a company that can successfully communicate via e-mail.