Blocked emails - UK Business Forums

I have recently sent an email to our customers informing of our new bank details. There were approx 500 email addresses I sent this email to, using Outlook Express and the Bcc function (undisclosed recipients).

Since doing this some of our customers and suppliers have incorrectly blocked our emails, so I am getting message failed every time I send them an email. Some of these I didn't even send the "bank details" email to in the first place.

Can anyone suggest anything I can do to prevent this happening?

Many thanks!

Source: http://www.ukbusinessforums.co.uk/forums/showthread.php?t=274372

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