Outgoing email not working from on site


I'm trying to troubleshoot a problem with outgoing email that popped up this morning, and I am running out of ideas. About 7:30 this morning, Internet access for the site went down. We called our ISP, they said they were having an issue, and they sent a tech on site who fixed it. However, since then, our email (outgoing) hasn't been working. First, a little information about the site and how things are set up:

Office with about 30 users, all running Outlook clients (versions vary from 2007 on a few to 2013 on most).  We have a SonicWall TZ205W appliance with Comprehensive Gateway Security Suite enabled behind the ISP's router. We don't host our email on site (it's run through our web hosting provider). We are sending on port 587 (although I have tried switching around the settings for one of the users like using port 25, trying 465 TLS, etc, all with the same results).

Users can send/receive email just fine if they send from the "webmail" option through the hosting company. Users who have laptops can also send/receive from Outlook just fine, as long as they carry those laptops off site. One guy was unable to send/receive from his desk at the office with Outlook, but the messages he had stuck in his outbox all went out once he took the laptop home. This tells me something on site is wrong.

The ISP swears up and down it's nothing to do with them, and the hosting company swears up and down it's nothing to do with them. According to mxtoolbox.com, the domain is not on any blacklists and passes all SMTP tests they have.

From on site, I can telnet to smtpout.secureserver.net on port 25 and send if I authenticate with my GoDaddy account, but I can't do that from a POP client on any workstation.

I've done a little testing on site with my laptop (plugged into the 24-port switch behind the SonicWall) and Mozilla Thunderbird, which has a couple of accounts configured.

GoDaddy account - (using 587 for outgoing) I can receive but can't send.
Gmail account - (using 465/TLS for outgoing) I can both send and receive.

Interestingly enough...when I tried to set up a POP account for one of the users here in Thunderbird, I get an error that the mail server settings couldn't be found, and it refuses to even set up the account. But if I carry my laptop offsite, I can set up the account in Thunderbird and send/receive from it just fine.

So...I am at a bit of a loss. The SonicWall isn't showing anything particularly strange. We run AVG antivirus, and AVG hasn't reporting anything strange. Also: plugging directly into the ISP's router (bypassing the SonicWall) with my laptop yields the same results described above.
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jhighwindAuthor Commented:
Ok....so....literally one minute after I posted this, one of the users said it's working again. Sure enough, all my testing from Thunderbird works now as well.

This is not the first time this has happened for this site. Email stayed down from the time our ISP's tech came over this morning (about 8:00am or so was when he got here and fixed the problem where we had no Internet acccess), and it just now started working again (12:19pm).

So...I'm not really sure what to make of it, but the problem apparently fixed itself.
JohnBusiness Consultant (Owner)Commented:
When you send email, you need IP SMTP address, Authentication, and Ports (SSL) all correct.

I wonder if there was a DNS or like issue that took a couple of hours to promote through the system and fix itself. Since it is now working and you did not change the things in my first line, then I think it must have been the change filtering through.
jhighwindAuthor Commented:
So, it is apparently going on again this morning. Was fine all day yesterday (up until the last user left around 7:00 or so). People came in this morning, and the same thing is happening. Internet access is fine, just no email.

The odd thing about this is that the outgoing messages aren't even trying to go out at all, but they're just piling up in the outbox (for all users). So it's not like the emails are going out and sending back NDRs or anything. When this problem "resolved" itself yesterday, all the users who had messages stuck in their outboxes reported that the messages finally went out.

I'm about to head over there and see what other testing I can do.

edit: and more fun. Got there, and things are fine again. So people came in around 7:00 this morning and saw the exact same symptoms as yesterday, but just like yesterday, the problem worked itself out. Although it didn't take as long day (started working again by around 9:00, where it was after 12:00 yesterday).
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JohnBusiness Consultant (Owner)Commented:
You have some sort of connectivity problem or mail would not go out at all.

Look at the Anti Virus you use. Check firewall settings for time of day settings (I have never done a thing like that). Is your server set to not allow people at certain times of day. Look for those things.

Ask your ISP about their settings.
jhighwindAuthor Commented:
We definitely don't have any kind of "time of day" settings going on, and the anti-virus we use isn't showing anything abnormal (we run AVG Business Edition with the Remote Admin server that monitors/controls all the clients). When this happens, it happens to everyone on the LAN.

I actually did try temporarily replacing the SonicWall with a "dumber" router that doesn't have all the security features, and the problem also occurred at one point while that router was in place. Once I saw that the problem occurred regardless of which router I was using, I put the SonicWall back in place.

It's actually not the first time this problem has happened at that site. Last occurrence was...I want to say around May 2015. Exact same symptoms as what I described above, where outgoing email would stop working, then work itself out again. Happened over a period of a couple of days, had me pulling my hair out and going back and forth with the ISP as well as the hosting company, and seemingly worked itself out. I didn't think anything else of it until it happened again yesterday.

It has also gone down (stayed down for about an hour) and started working again since my last post here today. One of the users took his laptop (that has Outlook configured) home with him. Email didn't work from the laptop while he was on site, but it worked fine once he took it home (no changes to Outlook configuration at all during this time).

I'm going back and forth with the ISP at this point. They swear up and down that it has nothing to do with them, but I'm not too sure what else could be going on. I'm also cranking up the logging on the SonicWall for tonight to see if it picks up anything weird.

Another thought: It feels like the port we use for outgoing email (587, which is what our hosting provider wants us to use) doesn't work while this is going on. I don't feel like it's a blacklist, because I'd expect that to show up on something like mxtoolbox (or at the very least, messages would be getting past the outbox for the users instead of piling up/getting stuck in there like they have been).
JohnBusiness Consultant (Owner)Commented:
Check all the email settings in AVG in case it is trying to trap email.

We definitely don't have any kind of "time of day" settings going  <-- I am sure you are correct but we should ask.

So let us know from the more detailed logging. It would appear to somehow be connectivity. Settings are not usually "intermittent".
jhighwindAuthor Commented:
I have identified one device that appears to be a bandwidth hog over the last couple of days since I cranked up the logging/reporting settings. It's actually an ipad, and nothing else on the network is using a tenth of the bandwidth that it has been using over the last couple of days. Aside from that, I haven't seen anything particularly abnormal in the SonicWall's logs.

I can't say for sure if that's my problem, but the iPad's bandwidth usage is completely dwarfing everything else. So I've set up a rule to block it and will see what happens.

The problem with email is still occurring, but it seems like it has gone down in both frequency and length of downtime. Yesterday, the users came in early morning and noticed email wasn't working, but things came back up less than an hour later and didn't go down again for the rest of the day (as opposed to going down for 2-3 hours multiple times a day like it was before).
JohnBusiness Consultant (Owner)Commented:
I would say, based on the above, the it is your network, usage and congestion causing the problem. I cannot think of anything in Outlook or any setting that would cause this. Also see if congestion is actually knocking out your network from time to time.

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jhighwindAuthor Commented:
I'll keep an eye on things over the next few days. So far, it appears that email is the only thing affected when the problem occurs (Internet access and file shares + a few client/server applications they run on the LAN continue to work without issues when email goes down).

As it stands, I think I agree with you that something weird could be going on with the network because there aren't many other explanations I can think of that make sense considering the random nature of the problem. I don't feel that the hosting company is doing anything strange, because the users who carry their laptops offsite would have issues too. Whatever's going on here, it's only affecting on-site users.

The ISP.....I still have some suspicions, but they've escalated it up as high as their support chain goes (and their support is pretty good), and they swear up and down they have absolutely nothing whatsoever to do with the problem, so that one is a little hard to pursue. I don't suspect an RBL, because I'd think that would show up on mxtoolbox (and even in that case, the emails would actually go out and bounce back instead of getting stuck in outboxes and not going anywhere while the problem occurs). It seems that Outlook just times out trying to connect to the SMTP servers on any port while this happens.

At this point, the problem hasn't occurred again since my post yesterday. I'll keep the SonicWall's logging cranked up and report here if I see anything strange over the next few days.
jhighwindAuthor Commented:
Accepting John's solution for now, as the problem hasn't reoccurred since my last post. I'll open a new question and link back to this for reference if it pops up again.

In closing, I will mention this - for a software package that we use here, we had a conference room set up so that some people from the software company could assist with the install/configuration/training. They were here for the few days the problem happened. After they left, it hasn't happened again. So it may be possible that something was going on with them. But, at any rate, we seem fine now.
JohnBusiness Consultant (Owner)Commented:
@jhighwind - Thanks and I was happy to help you.
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