emails missing and failing to deliver using onpremisis exchange

For a couple of weeks I am having an issue with out exchange 2013 servers.

we have two exchange 2013 CAS servers and two Exchange 2013 mailbox servers. email to the internet is routed through cisco IronPort located in the DMZ. emails to the partner domains is routed directly through wan links and there are connectors for the partner domains.

we are receiving complaints from users that mails are not being delivered from partners domain to out domain and the some users have provided evidence of that. but when we test emails seems to be going but with some delay. it looks like emails with attachments are having issues more that emails without attachments. some emails are missing and not all mails.

there seems to be some problem now since a few days that emails sent to Hotmail are going in spam and some times emails to domains like Gmail are not being delivered (Authentication errors).

there has been no change from our side and now we are having all these issues.

as far as the dns name registration is concerned we have mx records configured only without spf records and it has been like this since the beginning. and we had no issues. fixing the spf records is gonna take time as we have to go through the HO.

I have this issue and lots of tickets related to these issues. any suggestions highly appreciated.
Aamer MAsked:
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David FavorLinux/LXD/WordPress/Hosting SavantCommented:
1) there seems to be some problem now since a few days that emails sent to Hotmail are going in spam...

This is because of Hotmail's content scanning or many other factors.

2) some times emails to domains like Gmail are not being delivered (Authentication errors).

This is because you're using an incorrect user/pass to relay through Gmail.

Keep in mind Gmail only allows relaying now for GSuite customers. Free Gmail accounts no longer allow relaying.

3) there has been no change from our side and now we are having all these issues.

Issue #1 is likely because of a Hotmail change.

Issue #2 is best debugged using SWAKS on the command line to verify you're using GSuite + user/pass being used is correct.
Aamer MAuthor Commented:
Thanks for the reply.

2. I am not relaying through gmail but I am sending emails from my domain to gmail addresses, some emails go through and some don't. on the ironport the emails that don't go through have errors related to authentication. there is no user name or password involded when sending to Hotmail.
DrDave242Senior Support EngineerCommented:
there seems to be some problem now since a few days that emails sent to Hotmail are going in spam and some times emails to domains like Gmail are not being delivered (Authentication errors)...as far as the dns name registration is concerned we have mx records configured only without spf records and it has been like this since the beginning.

Creating an SPF record will go a long way toward resolving the issues with outbound mail. In the long run, you'll benefit from setting up SPF, DKIM, and DMARC, but SPF is the simplest of these three and a good place to start. It won't have any effect on the issues you're having with inbound mail, but it may be sufficient to resolve your outbound issues.

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