We have been seeing this error on a few of our customers with WatchGuard XTM firewalls. The resolution is to disable deep inspection of SMTP.
Go to Firewall > Firewall Policies > (select the policy that controls outbound email) > Proxy Actions > TLS Encryption. Uncheck everything under "enable deep inspection of SMTP with TLS" and make encryption rules optional.
Repeat for the inbound policy.
Showing posts with label WatchGuard. Show all posts
Showing posts with label WatchGuard. Show all posts
Sender Email address with Apostrophe gives 550 Requested action not taken: mailbox unavailable
This was another fun one because there were no logs on the Exchange server to show it ever saw the message and my spam filtering service was passing the email and saying my Exchange 2010 server was responding with:
550 Requested action not taken: mailbox unavailable (in reply to MAIL FROM command)
The senders email address was like this first.o'last@domain.com which is technically a valid address but I frequently see admins remove the apostrophe to avoid complications.
I finally figured out that yes this error was happening where I suspected on our WatchGuard firewall. For some reason their SMTP proxy disallows this character by default even though it is valid. To fix:
550 Requested action not taken: mailbox unavailable (in reply to MAIL FROM command)
The senders email address was like this first.o'last@domain.com which is technically a valid address but I frequently see admins remove the apostrophe to avoid complications.
I finally figured out that yes this error was happening where I suspected on our WatchGuard firewall. For some reason their SMTP proxy disallows this character by default even though it is valid. To fix:
- Open WatchGuard System Manager then Policy Manager. Right click the SMTP-proxy rule then select Modify Policy option.
- lick the View/Edit Proxy button in the right side of Proxy action field.
- (Fix Sender) Mail From of the SMTP-proxy, click Change View button to switch to Advanced View. Click Edit button to edit the Non-allowed characters rule.
- Add the apostrophe at the end of default Regular Expression then click OK.
Change from [^-_.+=%*/~!&@?0-9a-zA-Z] to [^-_.+=%*/~!&@?0-9a-zA-Z'] - (Fix recipient) Rcpt To of the SMTP-proxy, click Change View button to switch to Advanced View. Click Edit button to edit the Non-allowed characters rule.
- Add the apostrophe at the end of default Regular Expression then click OK.
Change from [^-_.+=%*/~!&@?0-9a-zA-Z] to [^-_.+=%*/~!&@?0-9a-zA-Z'] - To enable save the config to the device.
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