Sean Wallbridge
If you are having difficulties *sending* email to a foreign domain (email address) *from* Exchange, here’s some suggestions for things to check/address.
1. Ensure you have a valid PTR record (reverse IP, defined with your ISP, not with your DNS provider) that returns the right value when someone performs an nslookup against your Public IP (and some are fussy enough to require that the record, such as mail.mycompany.com matches the SMTP greeting your Mail Server gives out when making an SMTP connection) – Mxtoolbox is a nice source for checking most SMTP issues in one place – http://www.mxtoolbox.com/diagnostic.aspx
2. Ensure you have a valid SenderID/SPF record – check your SPF record here http://www.mxtoolbox.com/spf.aspx. Microsoft recently retired their SenderID wizard, however this 3rd party one looks promising: https://www.unlocktheinbox.com/senderid-wizard
3. Ensure you aren’t on any black lists (RBLs) and as well, if you are using a residential class IP, you may find your IP *range* on the block list. Again, MXtoolbox is a good little resource for checking that – http://www.mxtoolbox.com/blacklists.aspx
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